A few points to remember
Lightning apps aren't available in Salesforce Classic.
Field help text is now available in Salesforce Lighting Experience.
You can create 40 lookup relationships on an object.
You can have a maximum of 26 roll-up summary fields on a master object in the case of a master-detail relationship.
A validation rule is the best way to make a field required.
You can have a maximum of five active lookup filters per object.
After the Winter'17 release, inline editing is now available in Lightning Experience.