Objective: We highlight some of the key discoveries and developments in the area of team performance over the past 50 years, especially as reflected in the pages of Human Factors. Background: Teams increasingly have become a way of life in many organizations, and research has kept up with the pace. Method: We have characterized progress in the field in terms of eight discoveries and five challenges. Results: Discoveries pertain to the importance of shared cognition, the measurement of shared cognition, advances in team training, the use of synthetic task environments for research, factors influencing team effectiveness, models of team effectiveness, a multidisciplinary perspective, and training and technological interventions designed to improve team effectiveness. Challenges that are faced in the coming decades include an increased emphasis on team cognition; reconfigurable, adaptive teams; multicultural influences; and the need for naturalistic study and better measurement. Conclusion: Work in human factors has contributed significantly to the science and practice of teams, teamwork, and team performance. Future work must keep pace with the increasing use of teams in organizations. Application: The science of teams contributes to team effectiveness in the same way that the science of individual performance contributes to individual effectiveness.