  Cool luminous giants, in particular asymptotic giant branch stars, are among
the most important sources of cosmic dust. Their extended dynamical atmospheres
are places where grains form and initiate outflows driven by radiation
pressure, leading to considerable stellar mass loss and the enrichment of the
interstellar medium with newly-produced elements.
  This review summarizes the current understanding of dust formation and winds
in such stars, sketching a system of criteria for identifying crucial types of
dust grains in the range of possible condensates. Starting with an overview of
the specific conditions for dust formation in cool dynamic atmospheres, the
role of grains as wind drivers, as well as their influence on observable
properties of cool giants and the circumstellar environment is discussed in
some detail. Regarding the literature, special attention is given to current
developments, e.g., the debate concerning the Fe-content and size of silicate
grains in M-type AGB stars which are critical issues for the wind mechanism, or
recent advances in spatially resolved observations and 3D modeling of giants
and their dusty envelopes.
