To track the history of changes to fields on records, you need to enable field history tracking on the object. You then specify which fields you'd like to track history on.
In this lesson, we create a couple of picklist fields. We will use these fields later to establish field dependencies.
Now that we have created a couple of picklist fields, we will now create a field dependency between them. One will be the controlling field and the other will be the dependent field.
In this lesson, we test our dependent picklists.
Resource:
Edit Custom Fields - https://help.salesforce.com/articleView?id=editing_fields.htm&type=5