Seeing and sensing single G protein-coupled receptors by atomic force microscopy

•G protein-coupled receptors (GPCRs) regulate key physiological processes and are therefore important drug targets.•Complementary approaches are required to obtain mechanistic insight into the structure-function relationship of GPCRs.•AFM-based approaches allow various properties of GPCRs to be directly observed and quantified in physiological conditions.•FD-based AFM can image single GPCRs at high-resolution and quantify the free-energy landscape of ligand-binding.•AFM-based force spectroscopy interrogates the physical and chemical properties of GPCRs.