One of the important feature added by the Microsoft Dynamics 365 is Entity Assets. To add this we just have to select Specific Entity Assets when we want to add any entity to a solution
With Entity Assets, we can now export solutions with following entity assets:
Relationships (1:N, N:1, N:N)
We still have the option to add the entire entity by checking the Add All Assets Checkbox at the top right corner, or we can select manually the specific asset by checking on the specific asset.
We can now publish the customization to reflect the assets in the solution.