Evolution seems to be constructive, over time leading from simple to complicated forms, from prokaryotic to eukaryotic cells, from single cellular to multicellular organisms, from solitary insects to colonies, from animal groupings to human society. Two fundamental operations employed by evolutionary construction can be distinguished -- ‘staying together’ (ST) and ‘coming together’ (CT). Staying together means that individuals form larger units by not separating after reproduction, while coming together means that independent individuals form aggregates. Staying together can lead to specialization and division of labor, but the developmental program must evolve in the basic unit. Coming together can be creative by combining units with different properties. Research interests: the role that each mechanism plays in construction, their interplay, their outcomes and their relationships to different types of cooperation. In particular, we are interested in CT in microbial communities both theoretically and experimentally.