The knowledge of the amount and nature of matter present in the Universe is undoubtedly one of the most relevant topics in astrophysics and cosmology. It started with the pioneering work of Zwicky in 1933, who found the need for a large amount of dark matter in the Coma cluster. An important step has been the recent finding through the observation of distant type Ia supernovae of the presence of a significant vacuum energy density causing an accelerating expansion of the Universe. Nevertheless, the nature of most of the matter in the Universe is still unknown. Its solution requires the interplay of several fields of astrophysics and cosmology as well as particle physics, all of which are covered in this volume: Cosmic Microwave Background radiation, large scale structures, galaxy clusters, intergalactic absorption, dark matter components of galaxies, globular clusters, supernovae of type Ia distance measurements, gravitational lensing, X-ray observations, Lyman-alpha observations, dark energy, direct detection of weakly interacting massive particles (WIMPS), detection of neutrino oscillations, particle candidates for dark matter, and Big Bang nucleosynthesis of baryonic matter.

Therefore, this volume presents a very useful synopsis of all constituents of matter in the Universe.