The human body defies imagination. We take it for granted. Seven billion on the planet all functioning identically yet 3.5 million men and 3.5 million women - 2 totally different but complementary sexes, and each body unique. How can that be?

The human body defies imagination. We take it for granted. Seven billion on the planet all functioning identically yet 3.5 million men and 3.5 million women – 2 totally different but complementary sexes, and each body unique. How can that be?