I have been most interested in the study of globular clusters (GCs), as GCs are the oldest stellar systems in galaxies and also fossil records of galaxy formation. I have studied the dynamical evolution of GC systems in both the Milky Way and M87. Based on my understanding of GC dynamics, I then have extended my interest in GCs to their cosmological origins. Now I aim to study the formation and destruction histories of GCs in a cosmological context, which can provide further information on the histories of galaxies and the Universe.