
Parton distribution and correlation functions describe the relation between a hadron and the quarks and gluons (or partons) within it, and carry rich information on hadron's partonic structure that cannot be calculated by QCD perturbation theory. In this talk, I will review what lattice QCD can and cannot do in calculating the nucleon structure, and demonstrate how to combine the strength of both lattice QCD and perturbative QCD to explore nucleon structure in a way complementary to what we have been doing with experimental data in last forty years.