  We report on a novel kind of transition in random lasers induced by the
geometrical confinement of the emitting material. Different dye doped paper
devices with controlled geometry are fabricated by soft-lithography and show
two distinguished behaviors in the stimulated emission: in the absence of
boundary constraints the energy threshold decreases for larger laser volumes
showing the typical trend of diffusive {\it non-resonant} random lasers, while
when the same material in lithographed into channels, the walls act as cavity
and the {\it resonant} behavior typical of standard lasers is observed. The
experimental results are consistent with the general theories of random and
standard lasers and a clear phase diagram of the transition is reported.
