  After sketching some historical events related to Yukawa and Tomonaga
concerning the birth of mesons, the author describes recent developments in the
spectroscopy of pion-nucleus bound states via "pion-transfer" reactions. The
role of pions as Nambu-Goldstone bosons in nuclear media is emphasized by
recently obtained experimental evidence for the partial restoration of chiral
symmetry breaking. New light is shed on Kbar mesons, which play a unique role
in forming dense nuclear systems. The basic unit, K- pp, is predicted to
possess a molecular structure with quasi-Lambda(1405) as an "atomic
constituent". We find here "super strong nuclear force" produced by a migrating
real Kbar meson in the Heitler-London-Heisenberg scheme in place of the normal
nuclear force mediated by Yukawa's virtual mesons.
