Introduction

Galaxies are vast cosmic islands of stars, gas, dust, and dark matter held together by gravity. Hubble’s keen eye has revealed intricate details of the shapes, structures, and histories of galaxies — whether alone, as part of small groups, or within immense clusters. From supermassive black holes at galactic centers to giant bursts of star formation to titanic collisions between galaxies, these discoveries allow astronomers to probe the current properties of galaxies as well as examine how they formed and developed over time.