Male and female reproductive systems allow human reproduction. Fertilisation occurs when a sperm and egg join to form an embryo. An embryo develops into an unborn baby in the uterus during pregnancy.

As more women have kids in their 40s ... It’s a grand experiment in human reproduction, and scientists don’t yet know what the result might be. So far, scientists have only scant evidence ...

Here, the funny parents of X (formerly Twitter) relate how their kids interpreted the miracle of human reproduction.