Deep and detailed discussions on chemistry, chemical physics, photoelectrochemistry, photophysics, photocatalysis and possible applications of nanostructured semiconductor materials have shown increasing interest in the matter by scientists representing various research areas as well as industrial enterprises. Indeed, solar energy conversion and chemical methods for its realization became very popular again after the ``great jump'' of renewable energy sources between the middle of the 1970s and the beginning of the 1980s. Several excellent books have been published over the past years, however, in these books no attempt was made to approach this research area from the point of view of classical chemical physics. With this book, the editors aim: a) to generate an adequate scope of the modern trends and data obtained during the last years in the area of chemical physics of nanostructured materials, in particular, nanocrystalline semiconductors; b) to select an equal mix of scientists from Western and Eastern countries, all of them experts in their respective research areas; and c) to present to the international scientific community many interesting and important results which have been obtained by former Soviet Union researchers, but are not well known because they had originally been published in Russian books and journals. This book will be interesting and useful for scientists working in the area of semiconductor nanotechnology, photoelectrochemistry, photocatalysis, photochemistry of water and air purification, as well as for graduate and post-graduate students who are planning to join these research areas.