Since the invention of hybridoma technology, methods for generating affinity reagents that bind specific target molecules have revolutionized biology and medicine.[1] In the postgenomic era, there is a pressing need to accelerate the pace of ligand discovery to elucidate the functions of a rapidly growing number of newly characterized molecules and their modified states.[2] Nonimmunoglobulin-based proteins such as DARPins, affibodies, and monobodies represent attractive alternatives to traditional antibodies as these are small, soluble, disulfide-free, single-domain scaffolds that can be selected from combinatorial libraries and expressed in bacteria.[3] For example, monobodies—highly stable scaffolds based on the immunoglobulin VH-like 10th fibronectin type III (10Fn3) domain of human fibronectin[4]—have yielded antibody mimetics that bind to numerous targets for applications including intracellular inhibition,[5,6] therapeutics,[7] and biosensors.[6,8] These 10Fn3-based ligands can be derived from highly diverse libraries using techniques such as phage, ribosome, mRNA, bacterial, and yeast displays.[9]