INTRODUCTIONFertilization occurs internally in Amphimedon and embryos are brooded in multiple chambers throughout the adult. Each chamber contains a mixture of developmental stages, from egg to late ring stages (i.e., prehatch late embryos). At the end of embryogenesis, swimming parenchymella larvae emerge from the adult. After several hours in the water column, the larvae settle and metamorphose into juvenile sponges. This protocol details how to obtain Amphimedon larvae and post-larvae/juveniles as well as embryos. Once isolated, these biological stages can be used for a variety of molecular and cellular analyses.