Markup heirarchy needs to be ``<div id="reveal"> <div class="slides"> <section>`` where the ``<section>`` represents one slide and can be repeated indefinitely. If you place multiple ``<section>``'s inside of another ``<section>`` they will be shown as vertical slides. For example:
```html
-<div id="reveal">
+<div class="reveal">
<div class="slides">
<section>Single Horizontal Slide</section>
<section>