When it is complete, the Human Cell Atlas will be a comprehensive searchable map of our cells — a “Google map for the human body.” By combining elegant science and painstaking work in the trenches, the Atlas will portray the basic unit of life in all its staggering diversity, including every cellular subtype, how one type of cell can become another type, which genes are switched on by which cells, and how the environment influences it all. Aviv Regev, the leading evangelist for the project, talks about the ambition and promise of this remarkable tool of personalized medicine. (Underwritten by Helmsley Charitable Trust)