From cookies and candies to balloons and cards, heart-shaped items abound this time of year. They're even in our blood. It turns out that the most abundant protein molecule in blood plasma—serum albumin (SA)—is shaped very much like a heart. This protein does an astounding array of tasks in our bodies, such as maintaining normal fluid pressure in our tissues and transporting many different types of molecules in our blood. By studying the structural features of various human and nonhuman SAs, researchers are gaining insights into the protein’s versatile roles and possible ways to harness them, such as to carry drugs to places where they're needed in the body.