Spontaneous broken symmetry occurs when a system possessing a certain symmetric property collapses into a vacuum state which does not possess the symmetric property.
To help explain spontaneous broke symmetry a common example is usually given; a ball sitting on top of a hill in a completely symmetric state. However, its state is unstable: the slightest disturbance will cause the ball to roll down the hill in some particular direction into its lowest energy state. At that point, symmetry has been broken. A symmetrical situation therefore collapses into an asymmetrical state.
Spontaneous broken symmetry conceals nature’s order under a seemingly jumbled surface. In 1960, Yoichiro Nambu formulated the mathematical description of spontaneous broken symmetry in elementary particle physics. The spontaneous broken symmetries which Nambu formulated, differ from the broken symmetries described by Toshihide Maskawa and Makoto Kobayashi. These spontaneous occurrences seem to have existed in nature since the very beginning of the universe and came as a complete surprise when they first appeared in particle experiments in 1964.