Recent progress in spin physics

In this talk, I will review some recent progress in spin physics, relevant to both longitudinal and transverse spin phenomena. In the first part, I discuss the spin structure of the proton, particularly in connection with the quark and gluon spin contribution which could be extracted from the longitudinal spin experimental data. In the second part, I discuss the single transverse spin asymmetry, particularly how to understand them in the QCD factorization framework. We will review the most important progress in recent years in connection with the universality and/or non-universality of the relevant parton distributions and fragmentation functions.