  This contribution reviews results from interferometric observations of
circumstellar disks around young stars of $\lesssim$3 M$_{\odot}$, performed
with the MIDI instrument operating in the 10 $\mu$m spectral region. Two main
topics, the disk structure on $\sim$1-10 AU scales and the dust properties in
the same region, are illustrated with several examples of MIDI studies,
covering various evolutionary stages. The spatially resolved observations
largely confirm SED-only based hypotheses on disk structure, yet also reveal
degeneracies that may occur in such SED modeling. The properties of the dust on
the disk surface show a strong radial dependence: the dust close to the central
star has generally larger grain sizes and in particular a much higher
crystallinity than the dust in more remote disk regions.
