  This paper reviews some recent work on the properties of the outer halos of
galaxies. I particularly focus on recent and upcoming advances made with the
study of globular clusters. Globular clusters can be observed out to ~100 kpc
from the centers of galaxies, allowing the study of galactic halos well beyond
the regions probed by many other techniques such as observations of the
integrated light of galaxies. In the few well-studied cases to date, the study
of globular cluster systems has provided dynamical evidence for dark matter
halos around elliptical galaxies, and demonstrated kinematic differences
between different globular cluster populations that shed light on the formation
history of their host galaxies.

Astrophysics