Nanotechnology involves the application of structures, characterization, design, devices, production, and systems at the nanometer scale. Nanomedicine is a term implying the application of nanotechnology (the technology that uses nanosized particles) for therapy and diagnosis of diseases. Nanomaterials have numerous applications in areas ranging from catalysis, photonics, molecular computing, energy storage, fuel cells, tunable resonant devices. This is due to an increase in reactivity when compared to their micro-sized counterparts since nanoscaled materials exhibit larger surface-to-volume ratio, which provides unsaturated and, thus, more reactive surface atoms. Nanoparticles have been considered for biological applications, such as drug delivery, biosensing, imaging, anti-tumor and anti-bacterial therapeutics. A wide range of nanocarriers (e.g., polymeric nanoparticles, metal nanoparticles, polymeric micelles, liposomes, and carbon nanotubes) has demonstrated significant potential in cancer-targeted delivery. Moreover, nanoparticulate drug delivery systems were used for targeting diseases of various organs and systems: skin, central nervous system, skeletal tissue, cardiovascular apparatus, diabetes and many others. This book gives an overview of current research on nano-bio interactions, with a focus on the effects of nanoparticle physical characteristics on their interactions with live cells. The potential of nanotechnology in modern therapy of human diseases and the recent advantages in this field are summarized. An overview of limitations facing nanotechnology-based therapies is presented.