Abstract
In tight, populous clusters, where despite the increased difficulty of doing precision photometry, age and initial composition are less likely to vary from star to star, not to mention the advantages of a common distance, uniform reddening and a decent statistical sample. Variations in the one main remaining principal parameter, the mass, allow one to scrutinize stellar evolution and the initial mass function. Ultimately, the knowledge gained from the study of individual stars in nearby, resolved clusters can be applied to distant, unresolved clusters. This is especially relevant to trace ages and composition, and hence formation and dynamics, of distant populous clusters as basic building blocks e.g., in proto-galaxies near the edge of the Universe.
