The size, and therefore the importance, of the population of compact, steep-spectrum, radio sources has only recently been recognised. While it is now clear that the extended steep-spectrum sources are powered by a pair of, originally anti-parallel, beams which transport energy to the outer lobes some 105–106 parcsec away, our understanding of the compact steep-spectrum sources is almost nil. This is largely because our radio maps have not had high enough resolution to show their structures in any detail. However 1.67 and 5 GHz MERLIN observations (resolutions 0″.25 and 0″.1) of the ~20 steep-spectrum 3CR sources whose LAS is ≲2″ have now allowed us to classify their structures, at least in broad terms. These MERLIN maps, and recent VLBI maps, show that while there is a wide range of structures - from colinear doubles to amorphous “blobs” - the “peculiar” structures are strongly concentrated in the objects whose optical counterparts are called QSO's.