Nanomedicine is a developing field that includes different disciplines such as material science, chemistry, and engineering and medicine devoted to the design, synthesis and construction of high-tech nanostructures. The ability of these structures to have their chemical and physical properties tuned by structural modification, has allowed their use in drug-delivery systems, gene-therapy delivery and various types of theranostic approaches. Colloidal noble metal nanoparticles and other nanostructures have many therapeutic and diagnostic applications. The concept of drug targeting as a magic bullet has led to much research in chemical modification to design and optimize the binding to targeted receptors. It is important to understand the precise relationship between the drug and the carrier, and its ability to target specific tissues, and pathogens to make an efficient drug-delivery system. This book covers advances based on different drug-delivery systems: polymeric and hyper-branched nanomaterials, carbon-based nanomaterials, nature-inspired nanomaterials and pathogen-based carriers.