To describe all the most import­ ant problems that motivated the physics of the 20th century would require many volumes. What the authors have sought to achieve in this book is to con­ centrate on the more funda­ mental issues and to trace their historical development. Whilst no aspect of modern physics is uninteresting, the topics covered here are certain to fascinate any reader, whether trained in physics or not. The achievements and promise of exciting fields — atomic physics, astrophysics, quantum theory, elementary particle physics, quantum elec­tronics, and nonlinear physics — are covered.No attempt has been made to restrain the authors to a dry presentation of the inception of a particular theme, they have striven to enlighten the logic of the evolution of each concept and foresee what direction the future may take.CONTENTSQuantum Theory. Origins and Growth M.A. ElyashevichThe Origins and Development of Modern Atomistics D.N. TrifonovState-of-the-Art in 'New Atom' Research V.I. Goldanskii and V.P. ShantarovichQuantum Electronics V.S. LetokhovNonlinear Physics. Stochasticity and Structures A.V. Gaponov-Grekhov and M.I. RabinovichPhysics and Astrophysics in the Late 20th Century. Development and Future Outlook V.L. GinzburgEDITORIAL BOARDYe. P. Velikhov, Mem. USSR Acad. Sc. A. S. Borovik-Romanov, Mem. USSR Acad. Sc. I. M. Khalatnikov, Mem. USSR Acad. Sc. S. R. Mikulinsky, Corr. Mem. USSR Acad. Sc.  A. T. Grigor'yan, D. Sc. (Phys.-Math.)  V. P. Vizgin, Cand. Sc. (Phys.-Math.)