Life begins with one embryonic cell, replicating over and over. And for the first time, scientists have created a roadmap showing how organisms develop from just one cell. They tracked hundreds of thousands cells in zebrafish and frog embryos over 24 hours. The study reveals how stem cells turn into more specialised cells, and eventually, into complex creatures. It’s a new way of understanding our microscopic origins, and it could lead to a greater understanding of a multitude of diseases.