Sylvius 4 Online provides a unique Web-based learning environment for exploring and understanding the structure of the human central nervous system. Sylvius features fully annotated surface views of the human brain, as well as interactive tools for dissecting the central nervous system and viewing fully annotated cross-sections of preserved specimens and living subjects imaged by magnetic resonance. Sylvius is more than a conventional atlas. The program also incorporates a Visual Glossary, a comprehensive, visually rich, searchable database of more than 500 neuroanatomical terms that are concisely defined and visualized in photographs, magnetic resonance images, and illustrations from the textbook Neuroscience, making Sylvius a single source for teaching and understanding the organization of the human central nervous system. System Requirements Sylvius 4 Online is a Web-based program that runs within an Internet browser and requires an active Internet connection as well as the following: Desktops/Laptops: Internet Explorer 9 or newer, Firefox 18 or newer, Chrome 25 or newer, Safari 5 or newer. (Latest version of Chrome recommended.) Tablets: 10-inch screen and 1GB of RAM recommended. (If using iPad, iPad 3 or newer recommended.) Older and/or smaller tablets may work, but performance may not be optimal.