  We present new results of a program aimed at studying the physical
properties, origin and evolution of those phenomena which go under the somewhat
generic definition of "low-ionization, small-scale structures in PNe". We have
obtained morphological and kinematical data for 10 PNe, finding low-ionization
structures with very different properties relative to each other, in terms of
expansion velocities, shapes, sizes and locations relatively to the main
nebular components. It is clear that several physical processes have to be
considered in order to account for the formation and evolution of the different
structures observed. We present here some results that are illustrative of our
work - on IC 4593, NGC 3918, K 1-2, Wray 17-1, NGC 6337, He 2-186 and K 4-47 -
and some of the questions that we try to address.
