From Cellular Diversity to the Roots of Variability

Single-cell analyses are propelling us ever closer to answering questions that have long-motivated research in cell and developmental biology. What is the range of cellular diversity? What defines a cell type? How do cell types evolve and differ between species? And how do individual cells of a given cell type differ from each other and for what purposes? Recent achievements offer glimpses of the vast panorama emerging from this rapidly moving field. Cell atlases are one foundational pillar of these efforts with new studies providing an in-depth look at cell type diversity in mice. The recently reported Tabula Muris used two ap-