The cells are sent messages continuously through the molecules. But scientists have detected that this function can also be performed by protons. For research, the intestinal cells of the worm Caenorhabditus elegans have been studied. When these cells release protons, they discover that the muscles of the area contract. To show that the true ones responsible for the contractions are protons, the intestinal cells of the worm have been modified to prevent them from releasing protons. A molecule molded to the worm is then injected. Scientists excite this molecule through the light releasing protons. Thus they have seen that by giving light to the worms, intestinal contractions occur.