ABSTRACT: The Big Bang model and its inflationary extension provide fascinating windows into very high energy physics and into the physics of fundamental particles. I will describe how the three observational pillars of the Big Bang model (the Hubble expansion, the cosmic microwave background and the light element abundances) can be used to constrain inflationary models (which often find their roots in particle physics) and deviations from the neutrino sector of the Standard Model of particle physics.