The pion is the central particle to relate the particle physics and

the nuclear physics through the chiral symmetry. The importance of

the pion is getting visible in the theory side in the recent years in

nuclear physics.

I would like to discuss our effort to treat the pion in the relativistic

mean field model, which is still on the way to complete the method for the

comparison with experiments. On the other hand, the non-relativistic

approach with tensor interaction demonstrates the importance of the pion

(tensor interaction) for spin-orbit splitting and the halo formation.

We hope to unify the particle physics (strong interaction physics) with

the nuclear physics through the chiral symmetry and its symmetry breaking.