Synthetic biology strives to engineer new molecular methods for investigation and regulation of mammalian cell processes. This thesis presents a new dimerization system, controlled by small molecules, based on separated single chain Fab variable fragments. To prove the concept, we chose the anti-β-estradiol single chain Fab variable fragment, fused to a firefly’s luciferase, which served as the reporter system. By adding estradiol in the media of mammalian cells, we successfully initiated the dimerization of the individually expressed light- and heavy- antibody chains. The MTT assay proved that the system functions even when the estradiol concentration is not toxic to cells. With this system, we could easily control cell processes such as transcription, protein localisation and cellular signallization. While we examined only one of the antibodies and ligands, the application of others can make this system universal.