New, powerful techniques are required to observe individual protein molecules and their interactions in situ, in order to analyze, with high precision, in which cells the interacting proteins are located, and in what sub-cellular compartments.To achieve specific detection, we have based our method upon Proximity-ligation assay (PLA) that converts the binding of a protein or a protein complex by a pair of antibodies into an amplifiable DNA molecule.The antibodies have attached to them short DNA strands, and are referred to as proximity probes.The format of proximity-ligation used for in situ detection, in situ PLA, generates a circular DNA molecule upon dual binding of proximity probes to different epitopes on a protein, or to adjacent proteins.