Successful embryonic development depends on a series of patterning and symmetry breaking events. Developmental patterning is often coordinated by organizers, specialized signaling centers that dictate cell fate outcomes in a position-based manner. Multiple developmental organizers have been characterized in the 100 years since Spemann and Mangold’s landmark experiments describing the main body axis organizer in amphibians. Self-organization can occur in early embryos and other simple structures via self-sorting of heterogenous cells into domains or spontaneous symmetry breaking. Now, new technologies, stem cell-based in vitro models, and comparative analyses are enabling deeper understanding of the core mechanisms underlying embryo patterning and organizer function. This collection will highlight studies that use creative approaches to identify new mechanisms for developmental organizers, shed light on how signaling directs patterning, or uncover how self-organization and symmetry breaking occur.