  Interferometric observations of stars in late stages of stellar evolution and
the impact of VLTI observations are discussed. Special attention is paid to the
spectral information that can be derived from these observations and on the
corresponding astrophysical interpretation of the data by radiative transfer
modelling. It is emphasized that for the robust and non-ambiguous construction
of dust-shell models it is essential to take diverse and independent
observational constraints into account. Apart from matching the spectral energy
distribution, the use of spatially resolved information plays a crucial role
for obtaining reliable models. The combination of long-baseline interferometry
data with high-resolution single-dish data (short baselines), as obtained, for
example, by bispectrum speckle interferometry, provides complementary
information and will improve modelling and interpretation.
