  We study bridging transitions between spherically and cylindrically shaped
particles (colloids) of radius $R$ separated by a distance $H$ that are
dissolved in a bulk fluid (solvent). Using macroscopics, microscopic density
functional theory and finite-size scaling theory we study the location and
order of the bridging transition and also the stability of the liquid bridges
which determines spinodal lines. The location of the bridging transitions is
similar for cylinders and spheres, so that for example, at bulk coexistence the
distance $H_b$ at which a transition between bridged and unbridged
configurations occurs, is proportional to the colloid radius $R$. However all
other aspects, and, in particular, the stability of liquid bridges, are very
different in the two systems. Thus, for cylinders the bridging transition is
typically strongly first-order, while for spheres it may be first-order,
critical or rounded as determined by a critical radius $R_c$. The influence of
thick wetting films and fluctuation effects beyond mean-field are also
discussed in depth.
