The ability to deliver highly efficient therapeutic compounds specifically to diseased sites is crucial for effectively treating all human illnesses. Unfortunately, conventional therapeutic strategies require unnecessarily high systemic administration due to non-specific biodistribution and rapid metabolism of free drug molecules prior to reaching their targeted sites. Using the tools of nanotechnology, drug delivery systems within the nanometer size regime can be developed to alter both pharmacological and therapeutic effects of drug molecules. Due to their small size, these novel DDS offer superior advantages, such as altered pharmacokinetic behaviour and improved payload, over traditional large-scale systems. In addition, the relative ease in modifying their surface chemistry permits the attachment of targeting and therapeutic molecules for specific therapeutic applications. Finally, complex nanostructures can be assembled using different building blocks with multiple functionalities ranging from targeting, detecting, imaging and therapeutic capabilities.