How does a tiny cluster of cells become an embryo with a head, trunk, and tail? And how do thousands of genes coordinate this development? A new imaging method makes it possible to visualize the activity of thousands of genes simultaneously throughout the entire zebrafish embryo. Using this technology, a research team at the University of Basel, Switzerland, has created an atlas of all genes and cells involved in turning a cluster of cells into an embryo. The work is published in the journal Science.