Abstract: Solitons are exceptionally long-lived, spatially localized lumps of energy density in a field — they can be found in high optics, hydrodynamics, Bose-Einstein condensates, energy physics and in cosmology. In this talk, I will argue that certain types of solitons, called oscillons, can arise in abundance in cosmology —  both at the end of inflation in the very early universe, and in dark matter in the present day universe. I will then show that the formation, clustering, and collisions of such solitons can lead to signatures in structure formation, gravitational waves, and potentially lead to highly energetic bursts of light. If some of these consequences are observed, they would provide important insight into the underlying nature of inflation, as well as dark matter.