In this colloquium, I will explain why tiny neutrino masses are a key
ingredient to explain the baryon asymmetry in the universe. The small
neutrino masses are elegantly explained by the Seesaw mechanism which
predicts large Majorana masses of the right-handed neutrinos. These
heavy Majorana fermions are nothing but sources of baryon asymmetry in
the universe. I observed the seesaw mechanism more than 40 years ago. I
will show you why I could find this mechanism, which I never explained
in such a public lecture beside a few small places. And I will show you
why I gave it the name “Seesaw Mechanism”.