  Several samples have been proposed in the last years in order to study the
properties of intrinsically small sources. In this paper, we review the
properties of the main samples that are currently available, both selected on
the basis of spectral index and of morphology. As a result of the work in this
area, large numbers of intrinsically small sources have been found. We
summarize the present status of hot spot advance measurements, listing 18
sources with available VLBI data. The mean hot spot separation velocity is
v_{sep} = (0.19 +/- 0.11)h^{-1}c and the kinematic ages span the range from 20
to 3000 years. Finally, we present a brief outlook on the use of future
instrumentation in order to improve our understanding of radio source
evolution. Prospects for VSOP2, e-VLA, e-MERLIN, LOFAR, ALMA, and Fermi are
suggested.
