Graphics use elements and spatial relations on paper to convey elements and relations that are visuospatial or metaphorically visuospatial. Comprehending elements and spatial relations from graphics is relatively easy. Inferences of direction and distance are also relatively easy, but inferences requiring spatial transformations are more difficult. Still more difficult, yet common in science, are inferences of function and process. Diagrams can be enriched to facilitate conveying functional information, but comprehension of function typically requires expertise. These conclusions will be supported with examples from cognitive science research in several domains.