  Stellar halos around galaxies retain fundamental evidence of the processes
which lead to their build up. Sophisticated models of galaxy formation in a
cosmological context yield quantitative predictions about various observable
characteristics, including the amount of substructure, the slope of radial mass
profiles and three dimensional shapes, and the properties of the stellar
populations in the halos. The comparison of such models with the observations
provides constraints on the general picture of galaxy formation in the
hierarchical Universe, as well as on the physical processes taking place in the
halos formation. With the current observing facilities, stellar halos can be
effectively probed only for a limited number of nearby galaxies. In this paper
we illustrate the progress that we expect in this field with the future ground
based large aperture telescopes (E-ELT) and with space based facilities as
JWST.
