A brief summary of the theoretical and experimental knowledge of the spin
structure of the proton is presented. The helicity distributions of quark and
gluons are discussed, together with their related sum rules. The transversity
distribution is also introduced with possible strategies for its measurement.
Novel spin dependent and \bfk_\perp unintegrated distribution and
fragmentation functions are discussed, in connection with a new and rich
phenomenology of transverse single spin asymmetries.Comment: 8 pages, 5 figures, talk delivered at GDH02, July 3-6 2002, Genova,
Ital