With a milliseconds-long flash of blue light, Yale University researchers regulated a critical type of signaling molecule within cell membranes, another illustration of the power of light-based techniques to manipulate cell functions and thus to study mechanisms of disease. One of the most innovative new research approaches of recent years is called optogenetics or the use of genetically encoded probes to make cell functions sensitive to light. The team combined a plant protein that is sensitive to blue light with enzymes that catalyze the metabolism of signaling lipids within the cell membranes. When the complex was expressed in animal cells, scientists changed properties of cells such as their shape or ability to move simply by using blue light. By turning off the light, the researchers were able to rapidly reverse the changes they induced. They were also able to regulate activities within a region of a cell by illuminating the area.