Today, antibody engineering for clinical applications is a rapidly progressing field of science and a big business. The basic functions of an antibody can be spatially differentiated and attributed to various structural domains of a molecule. Therefore, each of them may be an object for engineering with the aim of using a definite antibody function. In this sense, the potential of antibodies is unique. In this article, recent achievements and current problems of antibody engineering are briefly reviewed. The main attention is focused on a molecular constructor that allows for obtaining, with the help of a versatile barnase-barstar module, mono- and multiva-lent miniantibodies and their derivatives with outlined properties.