Most of my research involves observations of the oldest stars and star clusters in the Galaxy to better understand the first epoch of star formation in the Universe. Specific topics within this broad area are: making accurate measurements of the ages of Galactic and LMC globular clusters based on the "stellar evolution" clock, measuring ages of individual old stars using the abundance of radioactive Thorium and measuring the abundances of elements in extremely chemically deficient stars with the goal of identifying the nature of the first stars through their nucleosynthetic yields. Other interests include identifying the critical main-sequence star mass above which stars explode as core-collapse supernovae and below which they become white dwarfs. the dynamics of globular star clusters and some of the exotic products of stellar collisions, detailed tests of stellar evolution models, luminosity function of galaxies in clusters and compact groups.