  AGB stars, the precursors of Planetary Nebulae, exhibit high rates of mass
loss and eject material in the form of a slow (10-20 km/s), dusty molecular
wind. The general belief that the dust component of AGB circumstellar envelopes
have smooth density profiles and spherical symmetry have recently been shaken
by new high resolution images, showing that clumpy and asymmetric structures,
analogous to the ones observed in Planetary Nebulae, can be present even before
the end of the AGB. To illustrate how and when these structures appear, and
possibly to address the question of how they may shape the subsequent evolution
of these systems, we have started a campaign of mid-IR high spatial resolution
imaging of a selected sample of AGB targets. We want here to illustrate our
technique, developed for the mid-IR camera MIRAC3, and to show the first
results obtained at the NASA Infrared Telescope Facility.
