All biomass is derived from photosynthesis. This provides us with food fuel, as well as fibre. This process involves conversion of solar energy, via photochemical reactions, into chemical energy. In plants and cyabacteria, carbon dioxide and water are converted into carbohydrates and oxygen. It is the best studied research area of plant biology. We expect that this area will assume much greater importance in the future in view of the depleting resources ofthe Earth's fuel supply. Furthermore, we believe that the next large increase in plant productivity will come from applications of the newer findings about photosynthetic process, especially through manipulation by genetic engineering. The current book covers an integrated range of subjects within the general field of photosynthesis. It is authored by international scientists from several countries (Australia, Canada, France, India, Israel, Japan, Netherlands, Russia, Spain, UK and USA). It begins with a discussion of the genetic potential and the expression of the chloroplast geme that is responsible for several key proteins involved in the electron transport processes leading to O evolution, proton release and the production of 2 NADPH and A TP, needed for CO fixation. The section on photosystems discusses 2 how photosystem I functions to produce NADPH and how photosystem II oxidizes water and releases protons through an oxygen clock and how intermediates between the two photosystems are produced involving a two electron gate .