Project D -  Constructing HR Diagrams for Star Clusters out to Virgo.
Population synthesis studies promise an independent story of time evolution if we can reach the main sequence in Virgo. The suggested volume also includes enough examples to provide a "fair sample" of stellar populations. A 30 meter aperture is needed to do a complete study in a finite time (still years, however). High angular resolution is necessary to obtain accurate photometry and uncontaminated spectra of individual stars in a large sample of clusters in a large sample of galaxies, to study the history of element build up in the Universe and the constancy (or not) of the initial mass function.