17. Spontaneous Symmetry Breaking Emerges in Theory For Pions (1960)

Nambu relates the smallness of the pion mass to an approximate symmetry, which leads to an important insight: the symmetry of a physical system can be different from that of the interactions among the system’s components. Such “spontaneous symmetry breaking” is ubiquitous, occurring in, for example, magnets and solids. It is also related to the theory underlying the Higgs boson.

What is spontaneous symmetry breaking:

And I just keep this video here to learn later: