The Cosmic Microwave Background (CMB), relic radiation from the hot Big-Bang, carries a wealth of information about physical processes at work in the very early universe, at energies far beyond the reach of man-made particle accelerators. Next generation observatories are poised to further constrain physics beyond the Standard Model of particles and fields, the nature of Dark Matter and Dark Energy, the existence of primordial Gravitational Waves, and the formation of structures.