Human foetal genitalia. Coloured scanning electron micrograph (SEM) of the developing genitalia of an approximately eight week old human foetus. Up until about week 7 to week 8 of pregnancy, both sexes have what's known as a "genital ridge" an identical preliminary set of genitalia that will eventually differentiate to become either male or female sex organs. That means that sex organs come from the same foundations: The testes in men are equivalent to labia and ovaries in women, and the penis is the equivalent of the clitoris. The foetal feet are also visible in this image. Magnification: x12 when printed 10 centimetres wide.