  QCD instantons generate non-perturbative spin- and flavor- dependent forces
between quarks. We review the results of a series of studies on
instanton-induced correlations in hadrons. We first present some evidence for
instanton-mediated interactions in QCD, based on lattice simulations. Then we
show that the Instanton Liquid Model can reproduce the available data on proton
and pion form factors at large momentum transfer and explain the delay of the
onset of the perturbative regime in several hard reactions. We also show that
instantons generate a deeply bound scalar color anti-triplet diquark, with a
mass of about 450 MeV and size comparable with that of the proton. The strong
attraction in the anti-triplet scalar diquark channel leads to a quantitative
description of non-leptonic weak decays of hyperons and provides a microscopic
dynamical explanation of the Delta I=1/2 rule.
