This book is the outcome of a Bioenergetics workshop held at Nanyang Technological University (NTU), Singapore in April 2018 to honour Professor Bertil Andersson for his outstanding contributions to scientific research and administration, particularly his very successful 11 years a NTU as Provost (2007-2011) and President (2011-2018). The main focus of the book is on the mechanisms of photosynthetic oxygen production by water splitting and the reverse respiratory reaction of oxygen reduction to water. Also discussed is how these reactions can be used for the development of artificial photosynthesis for the generation of sustainable solar fuel. The various chapters are written by international experts including Nobel Laureates Rudolph Marcus and John Walker. They provide the very latest knowledge of how the flow of energy in biology is driven by sunlight and efficiently utilized to power life. This book is suitable for students and researchers who are interested in molecular details of energy flow on our planet and also concerned about sustainability of humankind.