Vanadium has long been known to mimic or to enhance insulin activity. It was estimated that by the year 2025 about 300 million people would suffer from diabetes mellitus. Diabetic patients are also subject to other pathologies such as nephropathy, arterial and neurodegenerative diseases. Behind the purpose to produce a special review book in inorganic biochemistry in the area of vanadium compounds/vanadate species, is the increase interest of vanadium knowledge, not only in chemistry but also in biochemistry, biology, toxicology, pharmacology and medicine. It was a wonderful opportunity to bring together remarkable contributions from many people that are responsible, at least in part, for the actual knowledge of vanadium in biological systems, as well for many papers highly cited and for an entire generation of scientists in the field. Personally, I consider myself a beginner in the Biochemistry of Vanadium, (I obtained my first decavanadate solution 51V-NMR spectra by 1985, at the University of Coimbra), and a product of the outstanding group of scientists and teachers that lead the way about 25 years ago, at the late 70´s and early 80´s. They are truly responsible for the actual interest of vanadium in fascinating and different scientific fields of research. The present book can be divided in two main parts: vanadium chemistry/biochemistry and biology/pharmacology/medicine, within the 16 chapters that wipe away the frontiers of 10 different countries. A special attention is given to decavanadate structure and chemistry, biochemistry (effects in muscle contraction/regulation) and in vivo biological studies. Also noteworthy are the chapters describing studies in aquatic organisms such as the ecophysiology perspectives of vanadium accumulation by ascidians, the use of fishes and fish cells lines for understanding the processes of vanadium in biology, as an alternative to mammalian systems, pointing out to a different interface of research. Medicinal applications of vanadium are push forward in chapters focusing structure-activity relationship of anti-diabetic vanadium complexes, vanadium compounds as anti-tumour drugs and anti-parasitic agents, improving bioactive ligands activity through complexation with vanadium, osteogenic action of vanadium compounds and cytotoxicity, in order to make vanadium available and safe for clinical use. Milestones in the history of vanadium biochemistry are also the chapters about the redox profile of vanadium, the role of vanadium in bromoperoxidases, the vanadium binding proteins in ascidians and more recently decavanadate interactions with lipidic structures. Putting it all together, this special Vanadium Biochemistry book would not be so special without the contributions of eminent scientists around the world, although some have been recently retire, such as the esteemed Professor Ramasarma and the esteemed Professor Sakurai. Thanking to all the contributors of the Vanadium Biochemistry book, clearly a wide-ranging and in many aspects an educational book that reflects, at least in part, the versatile and fascinating biochemistry of vanadium.