Scientists have published the first draft of the Human Cell Atlas, a comprehensive database of human cells that aims to understand the human body in health and disease. The atlas, created by an international collaborative consortium, includes more than 40 peer-reviewed papers covering a variety of tissues, cell types, and organs. One key advancement is the creation of the most complete intestinal cellular atlas to date, which has uncovered a type of intestinal cell that contributes to inflammation in diseases like ulcerative colitis and Crohn's disease. The atlas will impact biology and healthcare, leading to a new era of precision medicine.