The periodic table of human developmental factors includes ligands and extracellular regulators of the major signaling pathways that govern human development. Most of the ligands presented in the poster function either as morphogens, factors that direct cell fate and tissue morphology, or as growth factors, proteins that promote cell survival and proliferation. Research in model organisms has revealed that proteins belonging to the Hedgehog, Notch, Fibroblast Growth Factor, Wingless/Wnt, and TGF-beta families act as morphogens that regulate a number of developmental processes, including axis formation, anterior-posterior and dorsal-ventral patterning, limb bud formation, and lung, heart, kidney, bone, and cartilage formation. Morphogens promote or repress gene expression in a concentration-dependent manner to direct the collective response of groups of cells, which ultimately determines tissue organization. In addition to these proteins, development is dependent on a variety of different growth factors that promote the survival of specific cell populations at different stages of development. Both morphogens and growth factors are regulated by a number of proteins that either enhance or antagonize their activities. These proteins are categorized as regulators and are shown at the bottom of the table. The boxes are color-coded to indicate the different ligand families and the regulators that may alter their activities.