During this period the diagrams that convey the ideas of physics become more symbolic and less representational. Rutherford’s discovery of the atomic nucleus (1910), Niels Bohr’s model of the Hydrogen atom (1913), matter waves (1924), and the transition from an early universe with no Higgs field to a universe with a Higgs field (2012) are examples of this point. The photoelectric effect (1905), Brownian motion (1905), X-rays and crystals (1912), general relativity (1915), the expanding universe (1927-1929), and the global greenhouse effect (1988) remain accessible with a simple representational sketch.