The late 1970s brought opportunities to create proteins with new properties and, in particular, various derivatives of mouse monoclonal antibodies (mAbs) owing to the discoveries in molecular and cell biology and the development of bioengineering. Studies of mouse/human "chimeric" antibodies, miniantibodies to be synthesized in bacterial cells, full-size single-chain antibodies, complexes of miniantibodies with intramolecular chaperones, and other approaches made it possible to create a multitude of multifunctional biopreparations with predefined properties. The review describes, with the example of one research team, how studies in the field began and what the basis for their progress was.