One of the major goals of this book is to promote interchange among those fields of research, which have traditionally been cultivated by different communities of physicists. The contributions in the book help in obtaining deep comprehension of this new state of matter, a system of deconfined quarks and gluons. At the same time the book offers a few examples of how the seeds of the deconfined state are looked for in the phenomenological analysis of the observables measured in relativistic heavy ion collisions. The main topics are dealt with in a pedagogical style, suitable for beginners as well as experienced researchers.