Nan robotics is an emerging field of nanotechnology having nanoscale dimensions and is predictable to work at an atomic, molecular, and cellular level. The Nan robot skeleton is made up of carbon and its toolkit contains components like a medicine cavity containing medicine, a micro camera, a payload, a capacitor and a swimming tail. As nanorobots have special sensors i.e. physical or chemical which detect the target molecules in the human body can be used for the diagnosis and treatment of various vital diseases i.e. cancer, diabetes, atherosclerosis, haemophilia, kidney stones, etc. Nan robots to date are under the line of investigation, but some primary molecular models of these medically programmable machines have been tested. This review on nanorobots presents the various aspects allied i.e. introduction, history, ideal characteristics, Approaches in Nan robotics, basis for the development, tool kit recognition, and retrieval from the body, application considering diagnosis and treatment.