Researchers at the Allen Institute for Cell Science are working to understand the array of normal diversity in our own cells. They use human heart muscle cells, or cardiomyocytes, derived in the lab from human stem cells (specifically known as human induced pluripotent stem cells, or hIPSCs) to study some of this diversity as cells change state through a process known as differentiation. This image, taken by researchers on the Allen Institute for Cell Science’s Assay Development Team, shows two of the many different structures inside cardiomyocytes: the nucleus, in turquoise, which houses all the cells’ chromosomes; and the sarcomeres, in white, organized structures that are responsible for the muscle contractions that make your heart beat.