It would be impractical to put your entire app in a single component. Instead, we can import components from other files and include them as though we were including elements.
<script> tag that imports
import Nested from './Nested.svelte';
...then add it to the markup:
<p>This is a paragraph.</p>
Notice that even though
Nested.svelte has a
<p> element, the styles from
App.svelte don't leak in.
Also notice that the component name
Nested is capitalised. This convention has been adopted to allow us to differentiate between user-defined components and regular HTML tags.