This is not a lesson on Standard Model but for a quick idea, QUARKS make up hadrons of the universe and mesons too. Generally quarks of different flavors or colors combine to form a more complex elementary particle. A quark-anti-quark pair tend produce MESONS and TRIOS of certain quarks produce HADRONS. However only a certain combination of quarks in trios produce hadrons. Or do they?
In this article, it appears that as humans start questioning an observed rule of nature, nature confounds us again by agreeing with those who question the Trio rule of quarks/ A 4-quark particle? A 5-quark particle? The Quantum Framework, is, as always the most accurate theory ever made but an accurate theory on uncertainties. Read this article to start confounding yourself again. This is why I love physics
http://home.web.cern.ch/about/updates/2014/04/lhcb-confirms-existence-exotic-hadrons
other readings
http://lhcb-public.web.cern.ch/lhcb-public/
