  Some of the four-dimensional Superstring solutions provide a consistent
framework for a Supersymmetric Unification of all interactions including
gravity. A class of them extends successfully the validity of the standard
model up to the string scale ${\cal O}(10^{17})~GeV$. We stress the importance
of string corrections which are relevant for low energy ${\cal O}(1)~TeV$
predictions of gauge and Yukawa couplings as well as the spectrum of the
supersymmetric particles after supersymmetry breaking.
