If a user needs to define a section `foo` at a deeper level, they need to create
a directory named `foo` with an `_index.md` file (see [Branch Bundles][branch bundles]
for more information).
{{% note %}}
A **section** cannot be defined or overridden by a front matter parameter -- it
is strictly derived from the content organization structure.
{{% /note %}}
## Nested Sections
The sections can be nested as deeply as you need.
```bash
content
└── blog <--Section,becausefirst-leveldirundercontent/
├── funny-cats
│ ├── mypost.md
│ └── kittens <--Section,becausecontains_index.md
│ └── _index.md
└── tech <--Section,becausecontains_index.md
└── _index.md
```
**The important part to understand is, that to make the section tree fully navigational, at least the lower-most section needs a content file. (e.g. `_index.md`).**
{{% note %}}
When we talk about a **section** in correlation with template selection, it is
currently always the *root section* only (`/blog/funny-cats/mypost/ => blog`).
If you need a specific template for a sub-section, you need to adjust either the `type` or `layout` in front matter.
{{% /note %}}
## Example: Breadcrumb Navigation
With the available [section variables and methods](#section-page-variables-and-methods) you can build powerful navigation. One common example would be a partial to show Breadcrumb navigation:
Hugo will automatically create a page for each *root section* that lists all the content in that section. See the documentation on [section templates][] for details on customizing the way these pages are rendered.
By default, everything created within a section will use the [content `type`][content type] that matches the *root section* name. For example, Hugo will assume that `posts/post-1.md` has a `posts` content `type`. If you are using an [archetype][] for your `posts` section, Hugo will generate front matter according to what it finds in `archetypes/posts.md`.
