Custom Metadata Types: Relationship Field Enhancements, Long Text Areas

Build better apps with custom metadata types, and base your apps on types of metadata rather than just data. Check out the features that you’ve been waiting for, including metadata relationships to field definitions and long text areas in custom metadata types. These changes apply to both Lightning Experience and Salesforce Classic.
Available in: Professional, Enterprise, Performance, Unlimited, Developer, and Database.com Editions

Professional Edition orgs can create, edit, and delete custom metadata records only from types in installed packages.