The human heart is an amazing organ. Its muscle cells must contract in exquisite synchrony to pump oxygenated blood throughout the body. Now scientists have created a detailed map of cells in six regions of the heart. “For the first time, we have a zip code for each cell to know what population it belongs to,” said Christine Seidman, a cardiovascular geneticist at Harvard University and director of the Cardiovascular Genetics Center at Brigham and Women’s Hospital, in a recent statement. Seidman, who is also an investigator at Howard Hughes Medical Institute, and her colleagues described the heart atlas in September in Nature.

Understanding these cells and their functions in a healthy heart could help them determine what goes wrong in heart disease, the world’s leading cause of death. This video shows a beating heart with a protein involved in muscle contraction labeled in green.

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