Mesons, Baryons and Tetraquarks (IMAGE) Indiana University Caption A chart compares mesons, composed of two quarks; baryons, composed of three quarks; and the lesser understood tetraquark, composed of four quarks. Credit Fermilab Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.