What is that big collection of gas, dust, and stars floating far beyond Earth's atmosphere? It's a galaxy! With the help of vibrant images and factual, elementary-level STEM text, this nonfiction astronomy title for children examines the history of galaxies, their age, location, composition, and formation. It also explores how they were discovered. A space science feature spotlights galaxies as windows to the past. Captions, on-page definitions, additional resources, and an index support readers in grade 2 and up.