Algal biotechnology has come a long way since the early days of agronomy/mariculture for food use and the recovery of agars, carrageenans and alginates. Our increasing knowledge of algal physiology and biochemistry, combined with genetic engineering is opening up new vistas. The application of the ability to grow microalgae to very high yields in bioreactors, to a percentage of a theoretical maximum, as opposed to ponds, holds great promise for the future of algal biotechnology. At the macroalgal side possibilities on the horizon involve their use as a source of antifoulants, the possible use of sulfated polysaccharides in biomedical applications and the possibility of genetically engineering macroalgae to provide deterrence to microbial pathogens in mariculture. In the final analysis the expanded future of applying algal biotechnology for good, new and imaginative use must lie in ensuring that good science is tied to good economics. The present volume is a compilation of 20 chapters which discuss on the industrial applications in the field of biological nitrogen fixation, nutraceuticals and other bioactive compounds. Recent advances in cyanobacteria for bioactive compounds, active against a number of disease causing bacteria, viruses and fungi, their significant potential for colorants, polysaccharides, pharmaceuticals and pharmacological probes and also in the field of environment protection have been reflected in most of the chapters. This book will open a new vista in the field of algal biotechnology. The aim of bringing out of this book is to bring together the multi-disciplinary researches going around the world in the area of Algal Biotechnology and to disseminate information on the latest information on algae and this has been made possible only by the contribution of articles by the nationally and internationally acclaimed authors. The book will be useful to the students, teachers, scientists and researchers from the different branches of microbiology, plant science and biotechnology.