  The spin resolved current shot noise can uniquely probe the interactions in
mesoscopic systems: i) in a normal-superconducting junction, the spin current
noise is zero, as carried by singlets, and ii) in a single electron transistor
(SET) in the sequential regime, the spin current noise is Poissonian. Coulomb
interactions lead to usually repulsive, but also attractive correlations. Spin
current shot noise can also be used to measure the spin relaxation time $T_1$.
