Sensing small amounts of electron and nuclear spins has a very wide application in chemistry, physics and biology. In this work we plan to develop novel type of spin detection techniques, which will allow to reach ultimate sensitivity and detect a single electron and nuclear spins at ambient conditions as well at cryogenic temperatures. Moreover, since we use an atomic sized single optically active spin in diamond as detector, we will be able to image spins with nanometer resolution by using scanning probe techniques. In order to realize this goal, we will first theoretically design novel sensing methods that will not be disturbed by the presence of unwanted spin fluctuations. This will allow the detection of single spins of interest even in complicated biological environment, where the spin noise is unavoidable. These new techniques will be demonstrated experimentally by detecting spin labels on diamond in controlled conditions.