Countdown to life: The extraordinary making of you, BBC2: When the sexing of the body and the sexing of the brain don't match up

Countdown to Life again proved to be an extremely enlightening watch

The penultimate part of Countdown to Life: the Extraordinary Making of You on BBC2

It was all go on BBC2 for the penultimate part of Countdown to Life: the Extraordinary Making of You.

Part one covered the first eight weeks after conception, part two took us through the next 16 weeks inside the womb.

Perhaps the key development during this time – aside from the formation of the face – is the determination of a baby's sex. But as presenter Michael Mosley explained, sometimes the sexing of the body and the sexing of the brain don't match up.

Tragically, for some children this can lead to their feeling they have been born in the wrong body , while for the extraordinary "Guevedoce" (meaning "penis at 12") boys of the Dominican Republic, it can mean living the first 11 years of their life as a girl, only to physically grow a penis during puberty.

Countdown to Life once again proved to be an extremely enlightening watch and one that makes you realise just how incredible life – and the process of creating it – really is.