Countdown to Life: The Extraordinary Making of You

Michael Mosley tells the story of our first eight weeks - the most perilous time in the womb. This is when everything about who we are hangs in the balance - when the layout of our organs is determined, when our heart makes its first beat, and when the length of our lives could be decided. Told through a series of surprising, moving and inspirational human stories, we discover how the journey to becoming a human being is a rollercoaster ride where anything can - and does - happen.

Michael Mosley tells the story of our middle weeks in the womb - when we become an individual. At 8 weeks we all appear to be the same, but in the next stage of our development an incredible series of transformations takes place that makes each of us unique. Our instantly recognisable faces finish forming, we become left or right handed and our skin takes on its colour. Inside, we are developing our own bespoke immune system and as our brains are being organised, our personalities start to form. It's even believed that our feelings about sex and gender may be established long before we are born. Told through a series of surprising, moving and inspirational human stories, the show discovers that the path to becoming ourselves is mind-bogglingly complex - that there are an infinite number of possibilities that makes each of us unique.

In the last part of this epic series, Michael Mosley charts the final months of life in the womb when cartilage hardens to form the skeleton. We meet Janelly, who was born with no bones and who only survived thanks to an experimental drug.

The brain is developing rapidly too. 100 billion new connections each day are laying the foundations for memory. We meet memory man Joey, whose brain is incapable of forgetting anything he has experienced, which leads Michael to investigate exactly when our earliest memories are formed. Memories are created by what we experience through the senses and these too mature in these final weeks, though on the island of Pingelap, the sight of one in ten develops differently. These islanders are born profoundly colour-blind, which has given them a wonderful advantage in life. Finally, we witness the critical moment of the first breath and the beginning of a new life.

Produced in partnership with The Open University.