Whether it's our diets, building strength, or as part of medical advancements, it is no secret that proteins form an important part of our lives. Tracking how proteins work and move in cells, and purifying engineered proteins, are important tools for researchers. Traditional approaches to label proteins of interest, called 'tagging,' have the disadvantage of interfering with protein characteristics, including function and localization. Sometimes, these tags can also cross-react, which makes the information they provide nonspecific. A successful protein tagging system needs to be highly specific and have high affinity.