Twenty five years ago the first Russian papers dedicated to Surface Nonlinear Optics were published. This 25th anniversary allows us to look back on the early 1980s, the time of appearance of Surface Nonlinear Optics as a branch of Optics. Pioneering works by Prof. Y.R. Shen in the early 1980s, which were based on the 1960s fundamental ideas of Prof. N. Bloembergen, stimulated an explosion of such studies at Moscow State University and around the world.

Reaching the age of 25 is yet another occasion to sum up what has been done and to trace how this area was developed.