Amino acids are a fundamental building block for fur, muscle, and every other living tissue on Earth. These molecules come in “left-handed” (L) and “right-handed” (D) forms, a bit like gloves that fit different hands or mirror images. Life largely runs on the left-handed set, so biologists once assumed the right-handed versions were irrelevant. Yet nature quietly manufactures these D-amino acids and they can play a role in certain biological processes. In research led by Japanese analytical chemist Ren Kimura of the R&D-Analytical Science Research department of the Kao Corporation, Japan, researchers reveal that these overlooked molecules may offer an early-warning beacon for one of the most common and deadly ailments in cats, chronic kidney disease (or CKD for short), and they may even have potential in diagnosing human conditions.