And electrons. Amplify an energy difference/transfer to a shift in protein conformation, to the cellular-scale presence/absence of noticable molecules, to actio

And electrons. Amplify an energy difference/transfer to a shift in protein conformation, to the cellular-scale presence/absence of noticable molecules, to actions of cells that are collectively organized to respond, to tissues, to organisms. Optigenetic tools are just the most clear abstractions from photon->gene, but the same principles apply to thermo-, mechano-, chemo-, etc-, protien sensors (i.e. all of them). They're all an amplification cascade from photons and electrons upwards. It is elegant in how general that description is (and how it suggests an approach to synthetic designs).