After that very first moment, when sperm meets egg - the life of a human begins to unfold. But how does that one cell begin to divide and differentiate into the billions of complex parts of a human being. How much do those very first cells know? India Rakusen heads to a lab in Cambridge to look at a human embryo and speaks to leading cell biologist Magdelana Zernika-Goetz. And a baby isn’t a baby without the people and the world around it. We speak to Child psychologist Graham Music and historian Elinor Cleghorn about how intertwined we are with our world, and the instant effects on the mother. Presented by India Rakusen. Producer: Ellie Sans. Series producer: Ellie Sans. Executive producer: Suzy Grant. Original music composed and performed by The Big Moon. Mix and Mastering by Olga Reed. A Listen production for BBC Radio 4 and BBC Sounds