Galaxies are beacons that cosmologists use to chart the universe out to its remotest depths. Yet unlike a lighthouse, built on a sturdy pillar of rock, a galaxy resembles an island of light constructed on quicksand in a continuous state of flux. Galaxies are not isolated objects, but are surrounded by close companions, with whom they often maintain intimate and ongoing relationships. The oldest stars in a galaxy are nearly as old as the universe itself, and a study of their properties yields clues about how galaxies evolved in the distant past. The galaxies themselves define space in the expanding universe. In this article, I will describe current ideas on how galaxies originated and acquired their observed forms, and how this knowledge promises to lead to insights into the evolution of the large-scale structure of the universe.