A little essential oil trick you might not know about… 

You can use Lemon essential oil to help freshen and loosen the buildup inside your microwave.
Simply add 4 drops of Lemon essential oil to 2 cups of water in a microwave-safe bowl.

Microwave on high for 3 minutes, then let the steam do some of the work. Carefully remove the hot bowl and wipe down the inside.

 Less scrubbing.
 A fresh, clean scent.
 One more simple way to use what you already have at home.
 
Just remember: the bowl and water will be very hot, so use care when removing it.