Cell migration and cell rearrangement lie at the heart of tissue patterning, morphogenesis, cell immunity, and neural network formation. These cell dynamics involve highly coordinated regulation of F-actin and associated motor proteins most of which existed prior to branching of the Metazoa and its sister clades including the supergroup Amoebozoa. Co-option of the molecular toolkits underlying single-cell level behaviors such as cell migration and phagocytosis may have been critical for the evolution of complex and diverse multicellular assemblies. The Sawai lab studies self-organizing cell dynamics of the Amoebozoa species Dictyostelium whose unique conditional multicellularity involves cell-cell signal relay, cell aggregation, cell sorting and tissue elongation. By elucidating the roles of chemoattractants, cell-cell adhesion proteins and extracellular matrix in regulating cell polarity and movements, the team seeks to understand the common evolutionary path to the emergence of complex multicellular structures.