How does the foetus - a foreign body - survive inside the mother? The placenta is the extraordinary organ that allows this to happen; but this remarkable feat of evolution is only just being fully appreciated by science. Y.W. Loke explores the fascinating nature of the placenta and what it can tell us about evolution, development, and genetics. With his rich knowledge and experience, what Loke offers is tough-minded and valuable in understanding and unlocking many puzzles.