Anatomy is the identification and description of the structures of living things. It is a branch of biology and medicine. People who study anatomy study the body, how it is made up, and how it works.

The study of human anatomy reaches back thousands of years, to the Romans and Greeks. Herophilus, the Greek anatomist, is considered the first to take a scalpel to skin to see how our bodies work.

To arrive at these estimates, the authors of the new study, which was published Monday (Sept. 18) in the journal PNAS, considered the size and number of 400 types of cells in the body across 60 ...