Short answers, pulled from the story.
The Stanford Positron Electron Accelerizing Ring began its operations in 1972. This facility collided electrons and positrons with an energy level that allowed scientists to collect data about resulting particles.
Researchers earned the 1976 Nobel Prize in Physics for discovering the J/psi meson. The same detector later identified the tau lepton, which secured another Nobel Prize in 1995.
After collider operations ceased, the facility built for SPEAR was converted into a dedicated synchrotron radiation source known as SPEAR2. Scientists redirected their focus from high-energy collisions to studying materials with intense light beams.
A major upgrade of the ring completed in 2004 gave it the current name SPEAR3. This enhancement included improved capabilities for generating brighter and more stable light sources.
Physicists realized they were observing phenomena that had never been seen before because the charmonium states found within the data provided crucial evidence for the existence of the charm quark. These findings proved that the accelerator was capable of revealing fundamental building blocks of matter.