How to Navigate: A class hierarchy (ontology) allows you to retrieve information according to categories of interest. In the class hierarchy that follows, each line names a single class of biological objects. The levels of indentation indicate a subclass relationship to the class above. The numbers in parentheses indicate the number of instances of that class. Clicking on a class will display a page containing its instances (the biological objects that are direct children of that class). A class page also lists the parent classes and child classes, allowing you to navigate up and down in the hierarchy. Note: if the categories below are missing the expand icon, but you believe they they should be expandable, try reloading the page.