  The breaking of supersymmetry is usually assumed to occur in a hidden sector.
Two natural candidates for the supersymmetry breaking transmission from the
hidden to the observable sector are gravity and the gauge interactions. Only
the second one allows for supersymmetry breaking at low energies. I show how
the two candidates deal with the flavor and the $\mu$-problem; I also briefly
comment on the doublet-triplet and dark matter problem.
