© Wikimedia Commons, Creative Commons Attribution ShareAlike 3.0, Author: Headbomb, 21 January 2009.
This chart shows the known fundamental particles—those of matter and those of force. On the matter side, quarks and leptons are the constituents of larger and larger physical objects ranging from mesons to molecules. The forces are also associated with particles, as we will learn in this unit. The forces do not combine as easily as the matter particles: They unify with larger symmetries and grander theories. (Unit: 2)