The distribution of elements in the cosmos is the result of many different physical processes in the history of the Universe, from Big Bang to present times. Its study provides us with a powerful tool for understanding the physical conditions of the primordial cosmos, the physics of nucleosynthesis processes that occur in different objects and places, and the formation and evolution of stars and galaxies. Cosmochemistry is a fundamental topic for many different branches of Astrophysics as Cosmology, Stellar Structure and Evolution, Interstellar Medium, and Galaxy Formation and Evolution.

The advances made in the last decade of the XXth century in the study of the chemical evolution of the Universe have been really spectacular. On one hand, they have been brought by the availability of large-aperture ground-based telescopes and space borne telescopes (working in both the visible and other regions of the electromagnetic spectrum), and on the other hand by advances in theory and numerical modelling techniques in many fields of astrophysics such as stellar evolution stellar atmospheres, the physics of ionised plasmas and atomic and molecular physics.

According to the predictions of the most commonly accepted cosmological models, most of the light elements, especially deuterium and helium, were produced during the first minutes after the Big Bang. Comparison between observed and predicted lightelement abundances is one of the classical fundamental tests of cosmological models. Stellar evolutionary models have advanced considerably in recent years.