We performed imaging of semiconductor nanostructures (quantum wells and quantum wires) by atomic force microscopy of the cleaved edge of the samples under ambient conditions. Selective etching was used to enhance the composition contrast of the semiconductor heterostructure layers, and a procedure for retrieving the nanostructure dimensions from the scanned image is presented. The simple sample preparation and the relatively large (up to ∼100×100 &mgr;m2) imaged areas offer advantages over more conventional nanometer resolution techniques such as transmission electron microscopy. ©1995 American Institute of Physics.