 Thus halorhodopsin and channelrhodopsin together enable multiple-color optical activation, silencing, and desynchronization of neural activity, creating a powerful neuroengineering toolbox.Halorhodopsin from "Natronomonas" (NpHR) has been used to achieve inhibition of action potentials in neurons in mammalian systems.Since light activation of NpHR leads to an influx of chloride ions which is a part of the natural process for generating hyperpolarization, NpHR induced inhibition works very well in neurons.