> For the complete documentation index, see [llms.txt](https://docs.finngen.fi/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.finngen.fi/working-in-the-sandbox/which-tools-are-available/atlas/detailed-guide/how-to-define-a-cohort-in-atlas/concept-sets/viewing-the-hierarchy-of-standard-snomed-codes-in-atlas.md).
# View standard code hierarchy in Atlas
The medical code hierarchy is available in Atlas for [standard codes](/working-in-the-sandbox/which-tools-are-available/atlas/detailed-guide/code-sets-in-atlas.md). If you are using [non-standard codes](/working-in-the-sandbox/which-tools-are-available/atlas/detailed-guide/code-sets-in-atlas.md), you can [find equivalent standard codes in Atlas](/working-in-the-sandbox/which-tools-are-available/atlas/detailed-guide/how-to-define-a-cohort-in-atlas/concept-sets/find-mapped-equivalents-for-standard-and-non-standard-codes-in-atlas.md#find-the-standard-equivalent-for-non-standard-code) and then view the hierarchy of the equivalent standard codes.
### Viewing the hierarchy of a standard code
* Go to the **Concept Sets** page and select a Concept Set.
* Click a **Concept Name** to open the **Details** view.
On the **Details** page, you can see details of the medical code including **Vocabulary Id** (SNOMED in the example below) and **Standard Concept** that shows if the code is a standard code (Standard in the example below).
* Go to the **Hierarchy** page to see the parent(s) and descendant(s) (children) of the selected standard code.
### Parental codes
The Parent(s) of the code are shown in the **Parents** section. The parental codes can be added to the **Concept Set** (shown in the blue box) by selecting them using the **Id** column checkbox and clicking the **Add To Concept Set** button.
### Descendant codes
The **Children** section shows the descendants of the standard code in the code hierarchy. The descendant codes can be added to the **Concept Set** (shown in the blue box) by selecting them and clicking the **Add To Concept Set** button.