You can show the data type of fields in the project tree, which can be useful in many cases.
To enable this, click on View menu in the toolbar in the ribbon, and then click on Data Types ensuring that the check appears next to it.
You will receive a message that states that the project tree needs to be refreshed after you turn this option on or off. Clicking "Yes" will reload the project tree with the changes.
Once the project refreshes, the data type for each field in the data source, staging, and data warehouse tables will be shown in a parenthesis after the field name: