  We present an unifying description of a new class of localized states,
appearing as large amplitude peaks nucleating over a pattern of lower
amplitude. Localized states are pinned over a lattice spontaneously generated
by the system itself. We show that the phenomenon is generic and requires only
the coexistence of two spatially periodic states. At the onset of the spatial
bifurcation, a forced amplitude equation is derived for the critical modes,
which accounts for the appearance of localized peaks

Pattern Formation and Solitons