This research investigates group growth, in particular the transition from small to large groups. We focus on processes in small groups that enable such transition. Small groups are formed ?organically? around interactions and interdependencies. We aim to show that bystanders can get psychologically involved in this, even without participating actively. Through emotional ?contagion? and empathy, organic bonds can extend to bystanders. Psychologically, bystanders thus become part of an in-group. This process may, at a fundamental level, underpin a broad range of group growth phenomena and alter our understanding of large group formation.