A team from the German Cancer Research Center (DKFZ) has developed a strategy to make it possible to observe the evolution of certain chemical reactions—and quantify the results—in tissues of relatively large organisms. So far, this experimental strategy has been used in mice—animal models for the study of health problems in humans. Previously, it was only possible to observe the development of these chemical reactions in translucent organisms with few tissue layers, such as embryos of both fish and fruit flies. The group from DKFZ, including Brazilian researcher Letícia Roma, created rodents that were genetically altered to produce a phosphorescent protein sensitive to levels of oxygenated water (H2O2). These molecules are generated by a cell organelle—mitochondria—during the conversion of nutrients to energy. In small quantities, the molecule functions as an internal communicator; at high levels, it causes internal damage to the cell or even death. Scientists suspect that excessive production is responsible for an organism’s aging and the development of degenerative diseases. Using this strategy, which involves cryopreservation of the tissue and a chemical bath, the researchers measured the production of H2O2 during tumor development and an inflammatory reaction (Science Signaling, March 15, 2016). According to Roma, the group expects to use the technique to see whether alterations in the production of H2O2 are linked to diabetes.