Despite its small sea area, Hong Kong has an extremely rich marine biodiversity, comprising up to 25% of all taxonomic groups found in the greater China area. Have you ever wondered how these fishes, crabs, shrimps, snails, etc. got here? Where are they from? To address these questions of origin, we have to look into the life history of marine organisms. Many marine organisms spend part of their early life stages as plankton (organisms with relatively weak swimming ability th