A number of observed phenomena in high energy physics and cosmology lack their resolution within the Standard Model of particle physics. These puzzles include neutrino oscillations, baryon asymmetry of the Universe, existence of Dark Matter and inflation. We discuss the suggestion, based on the νMSM (an extension of the Standard Model by three light singlet fermions) that all these problems can be solved by new physics which exists only below the electroweak scale. We describe the formalism which allows to compute from first principles of quantum field theory and statistical physics the abundance of dark matter in this theory. Predictions of the νMSM are compared with results of different cosmological and astrophysical observations. © 2009 Elsevier B.V. All rights reserved.