Everybody knows you're not supposed to heat breast milk or formula in the microwave. Why not? The top two reasons usually cited are 1) it kills nutrients, which is scientifically unfounded, unless you're leaving it in there for 20 minutes, or 2) it creates hot spots, which can scald baby, which would be slightly plausible if we weren't talking about a liquid, which is going to have convection currents and is going to be thoroughly mixed long before it gets to baby's mouth.
No, the only real reason not to heat milk in the microwave is also the best one: because if you do, your baby's momma will kill you. She read all those reports on the internets and she doesn't believe your scientific mumbo-jumbo about upwelling for a minute.
So what's Daddy to do when baby is crying for food and Mommy's out at yoga? Just running hot water from the tap over the bottle takes forever and wastes a lot of water. It takes a while for the water to get hot and then most of the heat is just running down the drain.
Step 1: Heat Some Water in a Measuring Cup.
Grab the nearest Pyrex measuring cup. Put a couple ounces of tap water into it. Use the hot tap but don't wait for it to actually get hot--junior is hungry and time's a' wastin'! Stick the cup in the microwave for 1-2 minutes. You don't need a lot of water, because the bottle is going to displace a lot. You don't need a lot of time because, well, this is what microwaves are made for!