Planarians are freshwater flatworms that have powerful abilities to regenerate their bodies, which would seem to make them natural model organisms in which to study stem cells. But until recently, scientists had not been able to efficiently find the genes that regulate the planarian stem cell system. In this image, a single stem cell has given rise to a colony of stem cells in a planarian. Proliferating cells are red, and differentiating cells are blue. Quantitatively measuring the size and ratios of these two cell types provides a powerful framework for studying the roles of stem cell regulatory genes in planarians.

A sensor particle being engulfed by a macrophage—an immune cell—and encapsuled in a compartment called a phagosome. The phagosome then fuses with lysosomes—another type of compartment. The left video shows snowman-shaped sensor particles with fluorescent green nanoparticle “heads” and “bodies” colored red by Förster Resonance Energy Transfer (FRET)-donor fluorophores. The middle video visualizes light blue FRET signals that are only generated when the “snowman” sensor—the FRET-donor—fuses with the lysosomes, which are loaded with FRET-acceptors. The right video combines the other two. The videos were captured using epi-fluorescence microscopy.

More details can be found in the paper “Transport motility of phagosomes on actin and microtubules regulates timing and kinetics of their maturation” by Yu et al.

Glucose (top) and sucrose (bottom) are sugars made of carbon, hydrogen, and oxygen atoms. Carbohydrates include simple sugars like these and are the main source of energy for the human body.

Axolotls—a type of salamander—that have been genetically modified so that various parts of their nervous systems glow purple and green. Researchers often study axolotls for their extensive regenerative abilities. They can regrow tails, limbs, spinal cords, brains, and more. The researcher who took this image focuses on the role of the peripheral nervous system during limb regeneration.

This image was captured using a stereo microscope.

Related to images 6927 and 6932.

This is a super-resolution light microscope image taken by Hiro Hakozaki and Masa Hoshijima of NCMIR. The image contains highlighted calcium channels in cardiac muscle using a technique called dSTORM. The microscope used in the NCMIR lab was built by Hiro Hakozaki.

Scientists have long known that multicellular organisms use biological molecules produced by one cell and sensed by another to transmit messages that, for instance, guide proper development of organs and tissues. But it's been a puzzle as to how molecules dumped out into the fluid-filled spaces between cells can precisely home in on their targets. Using living tissue from fruit flies, a team led by Thomas Kornberg of the University of California, San Francisco, has shown that typical cells in animals can talk to each other via long, thin cell extensions called cytonemes (Latin for "cell threads") that may span the length of 50 or 100 cells. The point of contact between a cytoneme and its target cell acts as a communications bridge between the two cells.

Skins cells were reprogrammed into heart muscle cells. The cells highlighted in green are remaining skin cells. Red indicates a protein that is unique to heart muscle. The technique used to reprogram the skin cells into heart cells could one day be used to mend heart muscle damaged by disease or heart attack. Image and caption information courtesy of the California Institute for Regenerative Medicine.

Using techniques that took 4 years to design, a team of developmental biologists showed that certain proteins can direct the subdivision of fruit fly and chicken nervous system tissue into the regions depicted here in blue, green, and red. Molecules called bone morphogenetic proteins (BMPs) helped form this fruit fly embryo. While scientists knew that BMPs play a major role earlier in embryonic development, they didn't know how the proteins help organize nervous tissue. The findings suggest that BMPs are part of an evolutionarily conserved mechanism for organizing the nervous system. The National Institute of Neurological Disorders and Stroke also supported this work.

Disassembly of vasculature and reassembly after addition and then washout of 250 µM TBZ in kdr:GFP frogs. Related to images 3403 and 3404.

The marine bacterium Vibrio harveyi glows when near its kind. This luminescence, which results from biochemical reactions, is part of the chemical communication used by the organisms to assess their own population size and distinguish themselves from other types of bacteria. But V. harveyi only light up when part of a large group. This communication, called quorum sensing, speaks for itself here on a lab dish, where more densely packed areas of the bacteria show up blue. Other types of bacteria use quorum sensing to release toxins, trigger disease, and evade the immune system.

X-ray co-crystal structure of Src kinase bound to a DNA-templated macrocycle inhibitor. Related to images 3413, 3414, 3415, 3416, 3417, and 3419.

As this cell was undergoing cell division, it was imaged with two microscopy techniques: differential interference contrast (DIC) and confocal. The DIC view appears in blue and shows the entire cell. The confocal view appears in pink and shows the chromosomes.

These cells are induced stem cells made from human adult skin cells that were genetically reprogrammed to mimic embryonic stem cells. The induced stem cells were made potentially safer by removing the introduced genes and the viral vector used to ferry genes into the cells, a loop of DNA called a plasmid. The work was accomplished by geneticist Junying Yu in the laboratory of James Thomson, a University of Wisconsin-Madison School of Medicine and Public Health professor and the director of regenerative biology for the Morgridge Institute for Research.

A combination of protein structures determined experimentally and computationally shows us the complete metabolic network of a heat-loving bacterium.

The nucleolinus is a cellular compartment that has been a lonely bystander in scientific endeavors. Although it's found in a range of species, its function has been mysterious—mainly because the structure is hard to visualize. An August 2010 study showed that the nucleolinus is crucial for cell division. When researchers zapped the structure with a laser, an egg cell didn't complete division. When the oocyte was fertilized after laser microsurgery (bottom right), the resulting zygote didn't form vital cell division structures (blue and yellow).

The largest human cell (by volume) is the egg. Human eggs are 150 micrometers in diameter and you can just barely see one with a naked eye. In comparison, consider the eggs of chickens...or ostriches!

Ecteinascidin 743 (ET-743, brand name Yondelis), was discovered and isolated from a sea squirt, Ecteinascidia turbinata, by NIGMS grantee Kenneth Rinehart at the University of Illinois. It was synthesized by NIGMS grantees E.J. Corey and later by Samuel Danishefsky. Multiple versions of this structure are available as entries 2790-2797.

In 2006, scientists developed an optical microscopy technique enabling them to clearly see individual molecules within cells. In 2007, they took the technique, abbreviated STORM, a step further. They identified multicolored probes that let them peer into cells and clearly see multiple cellular components at the same time, such as these microtubules (green) and small hollows called clathrin-coated pits (red). Unlike conventional methods, the multicolor STORM technique produces a crisp and high resolution picture. A sharper view of how cellular components interact will likely help scientists answer some longstanding questions about cell biology.

Dynein (green) is a motor protein that “walks” along microtubules (red, part of the cytoskeleton) and carries its cargo along with it. This video was captured through fluorescence microscopy.

Cells in an early-stage fruit fly embryo, showing the DIAP1 protein (pink), an inhibitor of apoptosis.

Superresolution microscopy work on endoplasmic reticulum (ER) in the peripheral areas of the cell showing details of the structure and arrangement in a complex web of tubes.
The ER is a continuous membrane that extends like a net from the envelope of the nucleus outward to the cell membrane. The ER plays several roles within the cell, such as in protein and lipid synthesis and transport of materials between organelles. The ER has a flexible structure to allow it to accomplish these tasks by changing shape as conditions in the cell change. Shown here an image created by super-resolution microscopy of the ER in the peripheral areas of the cell showing details of the structure and the arrangements in a complex web of tubes. Related to images 5856 and 5857.

In vivo vascular development in kdr:GFP frogs. Related to images 3403 and 3405.

Mouse embryonic stem cells matured into this bundle of hair cells similar to the ones that transmit sound in the ear. These cells could one day be transplanted as a therapy for some forms of deafness, or they could be used to screen drugs to treat deafness. The hairs are shown at 23,000 times magnification via scanning electron microscopy. Image and caption information courtesy of the California Institute for Regenerative Medicine.

Fat tissue from the abdomen of a genetically mosaic adult fruit fly. Genetic mosaicism means that the fly has cells with different genotypes even though it formed from a single zygote. This specific mosaicism results in accumulation of a critical fly adipokine (blue-green) within the fat tissue cells that have reduced expression a key nutrient sensing gene (in left panel). The dotted line shows the cells lacking the gene that is present and functioning in the rest of the cells. Nuclei are labelled in magenta. This image was captured using a confocal microscope and shows a maximum intensity projection of many slices.

Related to images 6982, 6984, and 6985.

Model of a protein involved in cell division from Mycoplasma pneumoniae. This model, based on X-ray crystallography, revealed a structural domain not seen before. The protein is thought to be involved in cell division and cell wall biosynthesis.

The structure of the endothelium, the thin layer of cells that line our arteries and veins, is visible here. The endothelium is like a gatekeeper, controlling the movement of materials into and out of the bloodstream. Endothelial cells are held tightly together by specialized proteins that function like strong ropes (red) and others that act like cement (blue).

This image was part of the Life: Magnified exhibit that ran from June 3, 2014, to January 21, 2015, at Dulles International Airport.

A cancer cell with three nuclei, shown in turquoise. The abnormal number of nuclei indicates that the cell failed to go through cell division, probably more than once. Mitochondria are shown in yellow, and a protein of the cell’s cytoskeleton appears in red. This video was captured using a confocal microscope.

Serum albumin (SA) is the most abundant protein in the blood plasma of mammals. SA has a characteristic heart-shape structure and is a highly versatile protein. It helps maintain normal water levels in our tissues and carries almost half of all calcium ions in human blood. SA also transports some hormones, nutrients and metals throughout the bloodstream. Despite being very similar to our own SA, those from other animals can cause some mild allergies in people. Therefore, some scientists study SAs from humans and other mammals to learn more about what subtle structural or other differences cause immune responses in the body.

Related to entries 3744 and 3745.

This tropical scene, reminiscent of a postcard from Key West, is actually a petri dish containing an artistic arrangement of genetically engineered bacteria. The image showcases eight of the fluorescent proteins created in the laboratory of the late Roger Y. Tsien, a cell biologist at the University of California, San Diego. Tsien, along with Osamu Shimomura of the Marine Biology Laboratory and Martin Chalfie of Columbia University, share the 2008 Nobel Prize in chemistry for their work on green fluorescent protein-a naturally glowing molecule from jellyfish that has become a powerful tool for studying molecules inside living cells.

Ionic and covalent bonds hold molecules, like sodium chloride and chlorine gas, together. Hydrogen bonds among molecules, notably involving water, also play an important role in biology. See image 2519 for an unlabeled version of this illustration. Featured in The Chemistry of Health.

NIGMS staff are located in the Natcher Building on the NIH campus.

Pigment cells are cells that give skin its color. In fishes and amphibians, like frogs and salamanders, pigment cells are responsible for the characteristic skin patterns that help these organisms to blend into their surroundings or attract mates. The pigment cells are derived from neural crest cells, which are cells originating from the neural tube in the early embryo. This image shows pigment cells from pearl danio, a relative of the popular laboratory animal zebrafish. Investigating pigment cell formation and migration in animals helps answer important fundamental questions about the factors that control pigmentation in the skin of animals, including humans. Related to images 5754, 5755, 5757 and 5758.

This image is a computer-generated model of the approximately 4.2 million atoms of the HIV capsid, the shell that contains the virus' genetic material. Scientists determined the exact structure of the capsid and the proteins that it's made of using a variety of imaging techniques and analyses. They then entered these data into a supercomputer that produced the atomic-level image of the capsid. This structural information could be used for developing drugs that target the capsid, possibly leading to more effective therapies. Related to image 6601.

Ecteinascidin 743 (ET-743, brand name Yondelis), was discovered and isolated from a sea squirt, Ecteinascidia turbinata, by NIGMS grantee Kenneth Rinehart at the University of Illinois. It was synthesized by NIGMS grantees E.J. Corey and later by Samuel Danishefsky. Multiple versions of this structure are available as entries 2790-2797.

A humorous treatment of the concept of a cycling cell.

Mosquito larvae with genes edited by CRISPR swimming in water. This species of mosquito, Culex quinquefasciatus, can transmit West Nile virus, Japanese encephalitis virus, and avian malaria, among other diseases. The researchers who took this video optimized the gene-editing tool CRISPR for Culex quinquefasciatus that could ultimately help stop the mosquitoes from spreading pathogens. The work is described in the Nature Communications paper "Optimized CRISPR tools and site-directed transgenesis towards gene drive development in Culex quinquefasciatus mosquitoes" by Feng et al. Related to images 6769 and 6770.

The TRPA1 protein is responsible for the burn you feel when you taste a bite of sushi topped with wasabi. Known therefore informally as the "wasabi receptor," this protein forms pores in the membranes of nerve cells that sense tastes or odors. Pungent chemicals like wasabi or mustard oil cause the pores to open, which then triggers a tingling or burn on our tongue. This receptor also produces feelings of pain in response to chemicals produced within our own bodies when our tissues are damaged or inflamed. Researchers used cryo-EM to reveal the structure of the wasabi receptor at a resolution of about 4 angstroms (a credit card is about 8 million angstroms thick). This detailed structure can help scientists understand both how we feel pain and how we can limit it by developing therapies to block the receptor. For more on cryo-EM see the blog post Cryo-Electron Microscopy Reveals Molecules in Ever Greater Detail.

This video simulation shows what an uncontrolled outbreak of transmissible avian flu among people living in Thailand might look like. Red indicates new cases while green indicates areas where the epidemic has finished. The video shows the spread of infection and recovery over 300 days in Thailand and neighboring countries.

The G switch allows our bodies to respond rapidly to hormones. G proteins act like relay batons to pass messages from circulating hormones into cells. A hormone (red) encounters a receptor (blue) in the membrane of a cell. Next, a G protein (green) becomes activated and makes contact with the receptor to which the hormone is attached. Finally, the G protein passes the hormone's message to the cell by switching on a cell enzyme (purple) that triggers a response. See image 2536 and 2537 for other versions of this image. Featured in Medicines By Design.

This illustration represents the early life of a protein—specifically, apomyoglobin—as it is synthesized by a ribosome and emerges from the ribosomal tunnel, which contains the newly formed protein's conformation. The synthesis occurs in the complex swirl of the cell medium, filled with interactions among many molecules. Researchers in Silvia Cavagnero's laboratory are studying the structure and dynamics of newly made proteins and polypeptides using spectroscopic and biochemical techniques.

Multiple actin filaments (magenta) are organized around a dynamin helical polymer (rainbow colored) in this model derived from cryo-electron tomography. By bundling actin, dynamin increases the strength of a cell’s skeleton and plays a role in cell-cell fusion, a process involved in conception, development, and regeneration.

Cell-like compartments that spontaneously emerged from scrambled frog eggs, with nuclei (blue) from frog sperm. Endoplasmic reticulum (red) and microtubules (green) are also visible. Image created using confocal microscopy.

For more photos of cell-like compartments from frog eggs view: 6584, 6585, 6586, 6591, and 6593.

For videos of cell-like compartments from frog eggs view: 6587, 6588, 6589, and 6590.

This microscopic image shows a chromatin fiber--a DNA molecule bound to naturally occurring proteins.

Damage to each person's genome, often called the "Book of Life," accumulates with time. Such DNA mutations arise from errors in the DNA copying process, as well as from external sources, such as sunlight and cigarette smoke. DNA mutations are known to cause cancer and also may contribute to cellular aging.

Los ritmos circadianos son cambios físicos, mentales y conductuales que siguen un ciclo de 24 horas. Los ritmos circadianos típicos conducen a un nivel alto de energía durante la mitad del día (de 10 a.m. a 1 p.m.) y un bajón por la tarde. De noche, los ritmos circadianos hacen que la hormona melatonina aumente, lo que hace que la persona se sienta somnolienta.

Vea 6611 para la versión en inglés de esta infografía.

Multicellular yeast called snowflake yeast that researchers created through many generations of directed evolution from unicellular yeast. Cells are connected to one another by their cell walls, shown in blue. Stained cytoplasm (green) and membranes (magenta) show that the individual cells remain separate. This image was captured using spinning disk confocal microscopy.

Related to images 6969 and 6971.

Insects like the fruit fly use an elaborate network of branching tubes called trachea (green) to transport oxygen throughout their bodies. Fruit flies have been used in biomedical research for more than 100 years and remain one of the most frequently studied model organisms. They have a large percentage of genes in common with us, including hundreds of genes that are associated with human diseases.

This image was part of the Life: Magnified exhibit that ran from June 3, 2014, to January 21, 2015, at Dulles International Airport.

Crystals of fungal lipase protein created for X-ray crystallography, which can reveal detailed, three-dimensional protein structures.

Learn about basic science, sometimes called “pure” or “fundamental” science, and how it contributes to the development of medical treatments. Discover more resources from NIGMS’ Pathways collaboration with Scholastic. View the video on YouTube for closed captioning.

This image captures the many layers of nerve cells in the retina. The top layer (green) is made up of cells called photoreceptors that convert light into electrical signals to relay to the brain. The two best-known types of photoreceptor cells are rod- and cone-shaped. Rods help us see under low-light conditions but can't help us distinguish colors. Cones don't function well in the dark but allow us to see vibrant colors in daylight.

This image was part of the Life: Magnified exhibit that ran from June 3, 2014, to January 21, 2015, at Dulles International Airport.