Abstract: On October 8, 2019, it was announced by the Royal Swedish Academy of Sciences that the Nobel Prize in Physics 2019 was awarded to James Peebles for theoretical discoveries in physical cosmology and to Michel Mayor and Didier Queloz for the discovery of an exoplanet orbiting a solar-type star. Peebles has played a critical role in transforming cosmology into a precision science. We briefly review the foundation that Peebles laid for modern cosmology, focusing on his seminal contributions to our understanding of cosmic components, cosmic evolution, and cosmic structure formation.