Structural biology in situ - the potential of subtomogram averaging

► Subtomogram averaging from cryo-electron tomography data resolves structures in situ. ► Resolutions of 2-4 nm have been obtained in situ for a number of important structures. ► Structures include nuclear pores, viral proteins, vesicle coats, polysomes, flagella. ► Ongoing developments will improve resolution and allow wider application. ► Carrying out structural biology in situ has enormous potential.