The first collection of methods to study embryonic and fetal hematopoiesis in both invertebrate (fruit flies) and vertebrate (frog, fish, mouse, chick, and human) organisms. These state-of-the-art techniques range from the genetic, molecular, and cellular, to cell and embryo explant culture and whole animals, including in vivo imaging. Bioinformatic and functional genomic approaches for studying stem cells and their supportive stromal cells are also discussed. The protocols follow the successful Methods in Molecular Medicinea series format, each one offering step-by-step laboratory instructions, an introduction outlining the principle behind the technique, lists of the necessary equipment and reagents, and tips on troubleshooting and avoiding known pitfalls.