This collection of papers - starting with a brilliant article by one of the masters of the field - gives an excellent current review of our knowledge of matter. Partially basing his work on a variational formulation of quantum mechanics, E.H. Lieb links the difficult question of the stability of matter with important problems in functional analysis. In this collection the reader will find general results together with deep insights into quantum systems combined in papers on the structure of atoms and molecules, the thermodynamic limit, and stellar structure. The book is suitable as an accompanying text for a graduate course in quantum mechanics. This new edition contains significant new results on matter in magnetic fields.