During animal and plant development, cells self-organize into complex organisms, through the gradual refinement of cellular identities and their arrangement in space. This is an iterative process, which progresses through successive rounds of symmetry breaking, accompanied by changes in molecular and mechanical properties that feed back across multiple scales. Many of the elementary processes underlying developmental patterning and morphogenesis are now well documented, and a growing array of tools is available to observe and manipulate their dynamics. Yet, we lack a set of general principles that explain how they are coordinated in space and time to produce a defined outcome, and comprehensive synthetic approaches that use such principles to recapitulate development in vitro. This program will bring together experimentalists and theoreticians to work towards an integrated view of self-organization. This requires that we examine how the collective dynamics of development emerge from individual cellular behaviors - how cellular decisions in high-dimensional gene expression landscapes are coordinated in patterning, and how cellular force generation and mechanical feedbacks provide a substrate for tissue-scale communication and morphogenesis. Unifying these different processes, the notion of information may provide a common currency for the molecular and mechanical cues that guide development, encouraging us to consider that information is not only conveyed and interpreted but also self-organizes.