  Acoustics provides a powerful modality with which to 'see' the mechanical
properties of a wide range of elastic materials. It is particularly adept at
probing soft materials where excellent contrast and propagation distance can be
achieved. We have constructed a scanning acoustic microscope capable of mapping
the microstructure of such materials. We review the general principles of
scanning acoustic microscopy and present new examples of its application in
imaging biological matter, industrial materials and particulate systems.
