Biological processes are regulated with high spatial and temporal resolution. In order to manipulate them and understand the function of certain neural circuits, neuroscience goes beyond classical techniques in search of new methods, to answer questions that could not otherwise be solved. Light is the only external element that allows us to regulate these processes with precise control of essential parameters, such as space, time, and amplitude. The key element of these techniques lies in the photomodulator, as from its molecular design we can determine significant parameters for regulation, such as the bioactive half-life and the wavelength absorbed by the system. This paper looks at the azobenzene molecule, and explains the characteristics that can be modified in order to determine the parameters discussed.