Nanotechnology is the study of extremely small structures, having a size of 0.1 to 100 nm. The ideas and concepts behind nanoscience and nanotechnology were started by Physicist Richard Feynman. He described a process in which scientists would be able to manipulate and control individual atoms and molecules. Particles are engineered so that they are attracted to diseased cells, which allow direct treatment of those cells. This technique reduces damage to healthy cells in the body and allows for earlier detection of disease. An important application of nanotechnology in biomedical science deals with novel drug synthesis, drug delivery, imaging, gene therapy etc. Lipid and polymer-based nanoparticles are the most commonly used drug delivery systems. They offer several advantages such as improved drug solubility, preferential drug accumulation in tumor site, sustained drug release, improved bioavailability and biocompatibility over the conventional treatment methods. Nanoparticles also carry the potential for targeted and time-release drugs. Currently many substances are under investigation for drug delivery and more specifically for cancer therapy. An ideal drug-delivery system possesses two elements: the ability to target and to control the drug release. Targeting will ensure high efficiency of the drug and reduce the side effects, especially when dealing with drugs that are presumed to kill cancer cells but can also kill healthy cells when delivered to them. The reduction or prevention of side effects can also be achieved by controlled release. So Controlled drug delivery systems (DDS) have several advantages compared to the traditional forms of drugs. A drug is transported to the place of action, hence, its influence on vital tissues and undesirable side effects can be minimized.