This zebrafish with all its different cell types developed from a single cell, the fertilised egg
From fertilised egg to many specialised cells - life science news

Each new life starts with one cell, a fertilised egg, which will divide and produce more cells that each will take on a particular identity to form a brain, heart or muscle cell. A new study shows that finding cell identity not only depends on genetics, but also on signals from the environment of a cell that can be so strong that developing cells leave their migration path on the way to their final destination, and follow another path to e.g. another organ, thus taking on a new identity. These results, obtained in zebrafish embryos, contradict the idea that cells follow a fixed path to maturity and identity. Instead cellular differentiation appears to be more flexible than previously thought.

Read the full story: University of Basel
Scientific publication: Science