Written and edited by experts in the field, this collection from Cold Spring Harbor Perspectives in Biology explores how morphogen gradients are generated and interpreted during development. The contributors examine the regulation of morphogen synthesis, trafficking, and diffusion, as well as the complex webs of signaling mechanisms and transcriptional responses in recipient cells --whose fates are dictated by these morphogens. Including discussion of the roles of morphogen gradients in various tissues in organisms from yeast to humans, the volume is a vital reference for developmental biologists and cell biologists wishing to know how cell fate is determined during embryogenesis.