  A mechanism explaining a strong enhancement of nonleptonic weak decays was
suggested in 1975, later to be dubbed the penguin. This mechanism extends
Wilson's ideas about the operator product expansion at short distances and
reveals an intricate interplay of subtle features of the theory such as heavy
quark masses in Glashow-Iliopoulos-Maini cancellation, light quarks shaping the
chiral properties of QCD, etc. The penguins have subsequently evolved to play a
role in a variety of fields in present-day particle phenomenology. I will
describe the history of this idea and review its subsequent development. The
recent measurement of direct CP violation in K decays gives a new confirmation
of the penguin mechanism.
