The relationship between physical and chemical parameters sits at the heart of what this book is about. Recent advances in the synthesis of nanodiamonds either by HPHT or detonation are covered, along with extended characterization of the core and surface of nanodiamonds, focusing on the most advanced experimental tools developed for nanoscale diagnosis. Each technique presented includes presentation of both principles and applications. This combination of advanced characterizations offers readers a better understanding of the relationship that exists between physical and chemical parameters of nanodiamonds and their properties. In particular, the role of structural defects or chemical impurities is illustrated. Toxicity of nanodiamonds for cells is also discussed, as It is an essential issue for their bioapplications. Final sections in the book cover the main promising new advances and applications of nanodiamonds, the formation of hybrids, and their use in polymer and oil composites.