  We present first observations of the transversity parton distribution based
on an analysis of pion-pair production in deep inelastic scattering off
transversely polarized targets. The extraction of transversity relies on the
knowledge of dihadron fragmentation functions, which we take from
electron-positron annihilation measurements. This is the first attempt to
determine the transversity distribution in the framework of collinear
factorization.
