In this talk I will show how Cosmology can lead to discoveries of new fundamental physics, focusing on two concrete examples. First, I will show how CMB measurements can reveal the existence of new particles, such as the QCD Axion. Then I will review the case of Inflation, showing how it leads to the spectrum of the relic CMB and how it could lead to new predictions, such as extra relic Gravitational Waves or new signatures from nontrivial dissipative dynamics.