Once believed to be stable, the universe is expanding at an accelerating pace, propelled by dark energy and structured by dark matter. How do such concepts fit together? Serving as a guide to some of the most puzzling cosmological topics, astrophysicist Priyamvada Natarajan discusses the formation and growth of black holes, dark matter halos, the echo of the Big Bang, the discovery of exoplanets, and the possibility of other universes. Along the way, Natarajan also deepens our understanding of how radical scientific theories gain acceptance.