During development, an orderly structure progressively emerges as cells acquire more specialized identities and rearrange in space. Successive steps in this continuous process can draw on existing positional cues, but also self-organize as cells communicate through molecular and mechanical signals. Much is known about the relevant cellular and molecular processes, but the dynamics by which spatial patterns arise, and the underlying logic, often remain elusive. Drawing on several concrete examples, and a geometric approach to cell fate specification, in the spirit of Waddington‘s epigenetic landscape, I will discuss some of the ways that cell-cell interactions can support self-organization, and ask whether we should think of the form of an embryo as a consensus among its parts.