A growing number of newly developed fluorescent proteins (FPs) have biochemical properties that allow them to be regulated by specific wavelengths: Photoactivatable fluors are activated from a nonfluorescent (dark) to a fluorescent state by a specific wavlength pulse, photoconvertible can be converted from one color to another, and photoswitchable fluors shuttle between fluorescent and nonfluorescent states. Collectively these are called photocontrollable FPs. The table below also lists fluorescent Timers, which are able to change their emission wavelength over time.