More than a plugin, but not part of the jQuery core, jQuery UI enjoys a status as an official extension of the jQuery core library aimed at providing extended userinterface ( UI ) capabilities to jQuery-enabled web application pages. The tools available for us to use within the browser environment (JavaScript, DOM manipulation, HTML , and even the core jQuery library) give us low-level abil- ities to put together pretty much any kind of user interactions we might want toprovide for our users. But even so, building complex interactions using basic build-ing blocks can be a large and daunting task. The native JavaScript API for DOM manipulation is tedious in the extreme (luckily we have core jQuery to contend with that), and the set of form controls that HTML provides is rather sparse when com- pared with desktop environment counterparts. We can create our own interactions and controls (often called widgets) with the help of the jQuery methods we’ve learned to this point. But the jQuery UI library pro- vides us with a fair number of generally desired extended features or gives us higher-level building blocks to create them ourselves.