# Add entities to services

Copy as Markdown[View as Markdown](/docs/development/guides/resources/services/add-resources-to-services/add-entities-to-services.md)

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Once you have [created your entities](/docs/development/guides/resources/entities/create-entity.md) you can add them to your services.

To add an entity to a service you need to add the entity to the `entities` array in the service's markdown file.

/services/PaymentService/index.mdx

```

---
id: PaymentService
name: PaymentService
version: 1.0.0
# This assumes you have an entity called Payment
entities:
  - id: Payment
    # Optional, if not provided the latest version will be used
    version: 1.0.0
---

Your service markdown...
```

## Visualize entity relationships[​](#visualize-entity-relationships "Direct link to Visualize entity relationships")

**Added in** `eventcatalog@3.25.1`

When a service has entities assigned, EventCatalog generates a dedicated **Entity Map** page in the visualizer at `/visualiser/services/{id}/{version}/entity-map`. A link to this view appears automatically in the service sidebar under the visualizer section.

The entity map shows each entity as a node and draws edges between entities that reference one another using the `references` field in their properties. This gives you a quick overview of how the domain model is structured inside a service.

![Entity Map showing entity relationships](/assets/images/entity-map-e1404c5598cceb7732a548eae61bc0e6.png)

To learn how to define relationships between entities, see [model entity relationships](/docs/development/guides/resources/entities/model-entity-relationships.md).