There are three approaches to recognize the target site-First, as a point of comparison; the scientists use nanorobots small Brownian motions to find the target by random search. In a second method, it monitors for chemical concentration significantly above the background level. After detecting the signal, it estimates the concentration gradient and moves toward higher concentrations until it reaches the target. In the third approach, nanorobots at the target release another chemical, which others use as an additional guiding signal to the target. With these signal concentrations, only it passes within a few microns of the target is likely to detect the signal.