Some people already know this; this is for the people who do not. I had been eating leftover pizza for decades before it occurred to me. 

Specifically, I was home by myself and procrastinating about putting a cold slice in the toaster oven to make it become a warm and floppy slice, when the solution revealed itself: Use a skillet.

Instead of microwaving your leftover cold pizza to make soggy hot pizza, reheat the pizza slices in a large skillet on medium heat for 4-5 minutes. Make a lid for the pizza using aluminum foil.  This will help reflect the heat back to the toppings without trapping steam inside.

Chef John, from the culinary blog Foodwishes, claims that the residual oil from the pizza crust in your skillet will be reheated and make the crust crispy again and by the time this happens the cheese will have melted again and warmed the toppings. He even makes the claim that he uses this method with delivery pizza to improve the crust.

Would you reheat pizza or eat it cold?