The quark epoch ended when the universe was about 10−6 seconds old, when the average energy of particle interactions had fallen below the binding energy of hadrons. The following period, when quarks became confined within hadrons, is known as the hadron epoch.
The quark epoch came to an end when the universe reached an age of about 10−6 seconds, at which point the energy level of particle interactions fell below the threshold for hadronic binding. This led into a subsequent period known as the hadron epoch, where quarks were confined within hadrons.