Galaxies are are not simple superpositions of disks and spheroids. Instead, most disk galaxies host multiple faint stellar components. Studies within the Milky Way suggest that these additional components are old and chemically unevolved, and that they trace distinct epochs in the early history of the Galaxy. I will discuss recent work on the structure, kinematics, and stellar populations of thick disks and stellar halos, and the important constraints that they place on the assembly of disk galaxies.

Refreshments will be served at 3:30pm in the Steward Observatory Lobby.