  Modern redshift surveys enable the identification of large samples of
galaxies in pairs, taken from many different environments. Meanwhile,
cosmological simulations allow a detailed understanding of the statistical
properties of the selected pair samples. Using these tools in tandem leads to a
quantitative understanding of the effects of galaxy-galaxy interactions and,
separately, the effects quenching processes in the environments of even very
small groups. In the era of the next generation of large telescopes, detailed
studies of interactions will be enabled to much higher redshifts.
