Photoreactivity in a cell is modulated by incorporating an isolated optical trigger on the surface or in the membrane of the cell. Exposure of a cell bearing incorporated optical triggers causes the generation of a measurable physiological signal.
STATEMENT AS TO FEDERALLY SPONSORED RESEARCH
 This invention was made with United States government support under grant number DE-ACO5-00OR22725 awarded by the Department of Energy. The United States government has certain rights in the invention.