module that are different enough to require a submodule. Extension of the core module. (m-follow_twitter) ! *potential removal of this category ! Module Modifier ( .m-modulename.mm-modifiername ) ! This is used for small chainable changes to a module. Usually combined with module. (.mm-has-svg) ! State ( .is-statename ) ! State classes are used to represent different states of a module, not changes to the module. (.is-disabled)