Scientists from Academia Sinica and National Taiwan University, together with international collaborators, have developed a high-performance red fluorescent biosensor for lactate (lactic acid). The new biosensor, named R-eLACCO2, allows researchers to visualize how lactate levels change in real time inside living mice. When used alongside a green fluorescent biosensor, it opens up new possibilities for studying how metabolism and brain activity interact. The study is published in Nature Communications.