> 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/how-to-define-a-simple-icd-case-control-cohort-in-atlas/define-a-simple-icd-control-cohort-in-atlas.md).

# Define a simple ICD control cohort in Atlas

This example shows how to build a simple "all who are not cases" control cohort using the Finnish-specific H81 ICD10fi codes.

### Step 1: Clone the case cohort

* Click the **Cohort Definitions** on the left menu and open your case cohort (e.g. Test\_Cohort\_Cases\_MN):

<figure><img src="/files/bFIerfmOjo52UNXSvjGu" alt=""><figcaption></figcaption></figure>

* **Clone** the cohort by clicking the copy button <img src="/files/CzltblD4nehI81H0qbEY" alt="" data-size="line">
* The name of the cloned cohort is "COPY OF ...". **Rename** the cohort as the controls cohort (e.g. Test\_Cohort\_Controls\_MN)
* **Save** the cohort by clicking the save button <img src="/files/mnwt5JQuUzWerumFz7S6" alt="" data-size="line">

### Step 2: Change the Inclusion Criteria

* **Open** the **Inclusion Criteria** by clicking its name (e.g. TestPhenotypeCases). This will open the inclusion criteria specified for the cases cohort.

<figure><img src="/files/qzc9K9q7o1vLdYlQxp2h" alt=""><figcaption></figcaption></figure>

* **Rename the Inclusion Criteria** (e.g. TestPhenotypeControls).
* **Change the Inclusion Criteria** from **"at least 1**” to "**with exactly 0**” and leave all other settings unchanged:

<figure><img src="/files/BQqA1gzl8UQLkIG93fIY" alt=""><figcaption></figcaption></figure>

* **Save** the cohort by clicking the save button <img src="/files/mnwt5JQuUzWerumFz7S6" alt="" data-size="line">

### Step 3: Generate the control cohort

* Open the **Generation** tab and generate the cohort by clicking the **Generate** button next to the same FinnGen data release you used to create the case cohort (FinnGen CDM R11 in the screenshot below). The cohort generation will take a few minutes and the speed is not dependent on the size of the sandbox IVM.

<figure><img src="/files/VrqT033tEBuUGJ7GVJK1" alt=""><figcaption></figcaption></figure>

The control cohort is now ready. This cohort can (and should) be [explored within Atlas](/working-in-the-sandbox/which-tools-are-available/atlas/detailed-guide/cohort-characterizations-in-atlas.md) and used in [Cohort Operations](/working-in-the-sandbox/which-tools-are-available/cohort-operations-tool-co.md) and [Trajectory Visualization tool](/working-in-the-sandbox/which-tools-are-available/trajectory-visualization-tool-tvt.md). The cohort may also be [exported from Atlas](/working-in-the-sandbox/which-tools-are-available/atlas/detailed-guide/how-to-define-a-cohort-in-atlas/how-do-you-export-finngen-ids-for-an-analysis-cohort.md) for further analyses like those described in the [General Workflows for the most common analyses](/working-in-the-sandbox/general-workflows-for-the-most-common-analyses.md).