Plant hormones play an important role as signaling molecules in the regulation of almost all phases of plant development, from embryogenesis to senescence. In the past few decades, many structurally and chemically diverse low-molecular-weight compounds have been identified as plant hormones, including abscisic acid, auxins, brassinosteroids, cytokinins, ethylene, gibberellins, jasmonates, and salicylic acid. In addition to the "traditional" hormones, strigolactones, a group of terpenoids, have been identified recently as a novel plant hormone that inhibits shoot branching. It is anticipated that new hormones may be further discovered in the future. Besides these lipophilic hormones, small peptides also play key roles in regulating plant growth and development as signaling molecules, such as CLE and phytosulfokine. This website provides general information on lipophilic (non-peptide) plant hormones and their metabolic pathways.