Physicists long assumed that nature loves symmetry and is characterized by it. It was believed that nature resides in a kind of “mirrored world” where right and left changed places and matter was exchanged for antimatter, and natural laws would stand.
After it was discovered that the decay of certain particles (kaons) was asymmetrical, a mathematics-based explanation for this was presented by Makoto Kobayashi and Toshihide Maskawa in 1972 . The explanation meant that there must be at least 3 families of “quarks”  that form matter. This theory was later verified in another stunning demonstration of “the unreasonable effectiveness of mathematics in the natural sciences.”
The idea of broken symmetry was formally introduced into the Standard Model of elementary particles in 1960 by Nambu. His contribution along with that of Kobayashi and Maskawa, helped explain why all particles are not always symmetrical, which includes a differentiation between particles and their antiparticles. This differentiation is critical to the universe’s existence—matter and antimatter annihilate when they come in contact. Thus somewhere along the line, matter must have had an edge over its counterpart to form the cosmos we inhabit today. (Both were created in equal amounts in the big bang, some 14 billion years ago.). As Gunnar Öquist, secretary general of the Royal Swedish Academy of Sciences, quipped when he announce the prize, “Thanks to symmetry breaking, we sit here.”