  Using differential magneto-optical imaging, we address the question of
mesoscopic inhomogeneity in underdoped Bi-2212 single crystals. Among other
features, it is shown that an anomalous temperature dependence of the
penetration field and of the first order transition (FOT) field of the vortex
lattice in such crystals can be understood as arising from inhomogeneity. The
effect of chemical inhomogeneity and pinning on flux penetration and the FOT is
discussed.
