Geneticist Steve McCarroll wants to make an atlas of all the cells in the human body so that we can understand in precise detail how specific genes work, especially in the brain. In this fascinating talk, he shares his team's progress -- including their invention of "Drop-seq," a technology that allows scientists to analyze individual cells at a scale that was never before possible -- and describes how this research could lead to new ways of treating mental illnesses like schizophrenia.