Why Reheating Leftover Eggs Is Almost Always A Bad Idea
Eggs have a lot going for them: They are absolutely packed with vitamins and they're easy to work with, even for burgeoning chefs. After all, you only need a bit of milk and some vigor in your stirring arm, and your scrambled eggs are already on the road to greatness.
This is because when you reheat an egg, it changes in a few ways. The most noticeable way is that the egg will become much more rubbery in its texture, and it'll ruin your previously fluffy scrambled eggs. This happens because the process of reheating is basically further-cooking and, in the case of eggs, cooking them for too long will cause all of the moisture in them to dry up, making the texture much tougher. While stirring the eggs while reheating them on the stove or in between short microwave sessions can help, scrambling new eggs might take less effort than trying to salvage yesterday's breakfast.
Reheating eggs can make them change color
Rubbery eggs may be unappetizing, but it's not the strangest fate your microwave can bestow on a plate of leftover eggs. Overcooking eggs can also cause them to turn green. This color change is due to the sulfur from the egg whites reacting with iron in the egg yolks. Green eggs (without ham) can happen if they're overcooked via any method, but it's easiest to do with a microwave because of its uneven heating method. Thankfully the green tint is harmless. In fact, reheating eggs doesn't appear to reduce their nutritional value at all, so your eggs will still retain their vitamin A, B2, B12, and everything else.
Also, on one final, related note: There are certain types of eggs you should never stick in the microwave at all. These include unpeeled hard-boiled eggs and raw eggs with their shells intact. The reason for this is that it is entirely possible for eggs to explode inside a microwave due to the buildup of steam inside the shell while heated. Eventually, the pressure inside a sealed egg becomes so high that it causes it to burst. So, its a good idea to try and avoid any egg-splosions as it will make for a loud start to your morning, and create some cleaning to do before or after you eat.