ABSTRACT
This chapter summarises the main features of the Λ $ \Lambda $ cold dark matter (CDM) model. It discusses how, though the Λ $ \Lambda $ CDM model provides a perfectly consistent explanation of the cosmological observations, it contains ingredients that cannot be explained by the standard model of particle physics and fundamental interactions. Matter-antimatter asymmetry of the universe and models of baryogenesis is represented by the fact that cosmologists' observable universe seems to be made, barring small traces of anti-matter in cosmic rays, only of matter with no traces of anti-matter. A cosmological puzzle is understanding the nature of dark energy, the mysterious fluid driving the current acceleration of the universe. The cosmological puzzles show how cosmology is an incredibly powerful laboratory to test theories beyond the standard model and general relativity. The cosmological puzzles provide a new set of challenging questions to be answered not simply at a cosmological level but at a fundamental one.
