Green fluorescent protein (GFP) and related molecules have been important signal molecules for cell biologists because they emit a bright signal to mark the position of tagged structures as well as changes in calcium and proton concentrations. Related molecules even emit in different colors. Now Hendrik Dietz and Matthias Rief from the Technical University of Munich have given us a detailed look at the "energy landscape" of GFP with the promise that it may also be useful indicator for forces.2 In this context, energy landscape refers to a three-dimensional map of the energy levels of the molecule as it is transitioned from its native state to an unfolded state.