It is a long-standing need of the pharmaceutical industry, physicians, and patients to improve pharmaceutical formulations by establishing simpler, less expensive preparations and treatments, while reducing toxicity. This need can be met with the know-how of drug delivery science that has already made advance developments in improved delivery of injectibles, oral formulations, drug device implants, as well as topical and transdermal delivery formulations, especially in the case of drug delivery to the brain, an untouchable region by traditional drug delivery systems. The reason behind the failure of conventional delivery systems in reaching the brain is the blood brain barrier (BBB) composed of tight tissues making it impervious to outside agents. Nanotechnology has the potential to address and resolve this challenge and make brain a reachable target for drug delivery systems, by combining unique elements of size, surface activity and charge of nanostructures. Micro and nanoparticles have opened up unexpected ways in diagnostics and therapeutics in medicine. The previous treatment strategies in the fields of autoimmune diseases and cancer involved non-targeted treatment options with extensive "collateral damage." Nanodelivery of drugs is predicted to reduce this collateral damage, extend the drug's availability and effectiveness at the site, and reduce toxicity and cost with a high pay-off load. In this review we present the role of micro and nanoparticles in drug delivery and some applications in the health care fields.