In this three-part series doctors Chris and Xand van Tulleken explore how the human body grows and changes.

This first episode explains why human childhood is longer than that of any other creature on earth, and what triggers the changes that take place as a child matures.

Using high-end science and graphics we see the life of a stem-cell as it’s never been seen before and the very moment when sperm and egg first meet.

The van Tullekens also reveal the latest research into extending the stem-cell life and growing organs in the lab.