Charm quarks or c quarks are the third most massive of the six quarks. Like all quarks, they are thought to be so small that they can not be divided. (They are called elementary particles for this reason). Similar to up quarks, charm quarks have a charge of +2/3. Although charm quarks are not extremely common, they can be found in particles created by particle accelerators (which smash atoms together at extremely high speeds), such as J/ψ mesons, D mesons, and other charmed particles. Since they are fermions (particles that can not have more than one of that particle at the same place at the same time), charm quarks have a spin of 1/2.
The discovery of charm quarks – and J/ψ mesons – led to a rapid series of scientific breakthroughs. These events are known as the November revolution.