For many years, the only way that scientists could study cells was at the population level, averaging together many types of cells. While averaging is a useful measure, it’s inexact. This is why experimental biologists, computer scientists, and physicists have created a powerful new suite of genomic tools that can accomplish what averaging can’t — reveal the inner life of specific cells. Using “single-cell analysis,” scientists can understand which genes are turned on and off in individual cells, and even determine how this relates to diseases such as cancer. With this technology, scientists have now embarked on a massive, worldwide effort to identify every single cell in the human body.