To gain the practical approach for low dimension designing of electronic chips, SET is being used widely to provide nanoscience applications. SET (Single Electron Transistor) is a new kind of switching device that uses proscribed electron tunneling to amplify current. SET is to be considered as elements for future low power, high density integrated circuits reason for this of their the potential to involving only few electrons for ultra low power. In this paper, the author has studied about the single electron transistor being used in physics and various nanoscience applications. The operation as single electron transistor with its past is mentioned included with advantages, disadvantage and various applications of SET.