Theranostics, a harmonious merger of therapeutics and diagnostics, paves the path to personalized medicine. Theranostics plays a crucial role in steering every step of drug development process, primarily the biomarker discovery, target selection and validation of biomarkers, dose optimization and monitoring of the drug response. This book - a compilation of current status of the burgeoning progress in the field of nanotheranostics - presents multidisciplinary chapters focusing on advanced techniques for imaging, including the in vivo multimodal imaging of tumors, drug delivery, diagnosis and site-specific targeting. The book delineates the applications of different types of nanostructures, viz. liposomes, polymer-based nanoparticles, solid lipid nanoparticles, ceramic-based nanoparticles, albumin nanoparticles, superparamagnetic iron oxide nanoparticles, semiconductor nanoparticles, dendrimers, silica-based nanocomposites and carbon nanotubes in drug delivery and as novel theranostic systems. It also focuses on metallic nanoparticles such as gold nanorods-based contrast agents for optoacoustic tomography, photothermal therapy and preclinical investigations. Further, the advent of metallo-fullerenes and nano-shells, the most recently developed metallic nanoparticles, as newer strategies employed in the treatment of various cancers and as theranostics agents, is aptly described. Use of novel neurological models, proteomic-based biomarker identification for cancer diagnostics and the futuristic applications of nanoparticles as platforms for theranostics, consisting of nucelic acid-based therapies in dermatology, radiolabeling nanoparticles for in vivo molecular imaging and nuclear scintigraphy, are presented in this volume too. This book is an elaborated treatise for researchers, young and experienced both, to relish and savor the current status of theranostics and its various applications available today and imminent in the near future.