Sperm is critical for the fertilisation of almost every living organism on our planet, including humans. To reproduce, human sperm have to swim a distance equivalent to climbing Mount Everest to find the egg.

They complete this epic journey simply by wiggling their tail, moving fluid to swim forwards.

Though over 50 million sperm will fail to reach the egg — the equivalent to more than six times the entire population of London or New York – it only takes one single sperm in order to fertilise an egg that will eventually become a human being.

Sperm was first discovered in 1677 — but it took roughly 200 years before scientists agreed on how humans are actually formed.