Falsecolour scanning electron micrograph of human sperm migrating up the uterus. The sperm (blue) are motile and orientated in the same direction. They travel across a background of uterine mucosa cells (purple, pink). The hairlike surface of the mucosa gives sperm a chemical protection enabling them to reach & fertilize the female egg. The head of the sperm contains human genetic material; its whiplash tail provides movement. 200300 million sperm start the journey through the uterus and fallopian tubes, lasting 12 to 24 hours, but only a few hundred reach the egg. Magnification: x4000 at 4x5 inch size x2500 at 6x7cm size.