Microwave oven
A microwave oven is an appliance that uses radio-frequency waves to heat the water inside food directly. It heats food from within rather than with hot air.
Also called: Microwave cooker
By Andrew Cooks · Updated · 3 min read
At a glance
The microwave oven cooks by exciting water molecules with radio-frequency waves, invented after a radar engineer's chocolate bar melted in his pocket in 1945. It's safe, it doesn't 'nuke' nutrients (it often preserves them better than boiling), and modern kitchens underuse it.
What it does for you
Beyond reheating: it steams vegetables in their own moisture (nutrient-retention champion), 'toasts' spices in bloomed oil, poaches fish, crisps papadum, softens citrus for juicing, melts chocolate in controlled bursts, and par-cooks potatoes that finish crackling in the oven.
Cook's tip
For steamed vegetables, keep them damp and covered and microwave for 2 to 4 minutes. No pot is needed, and they come out greener and more nutritious than boiled ones.
Kitchen trivia
Did you know the microwave oven was invented because of a melted candy bar?
See the answerKey facts
- Origin
- Raytheon, Waltham, Massachusetts, USA
- Invented by
- Percy Spencer (patent 1945)
- Skill level
- Beginner
- Why cooks like it
- Speed: direct molecular heating skips preheating entirely
Common uses
Reheating and defrosting; steaming vegetables; melting butter/chocolate; softening brown sugar and butter; quick 'baked' potatoes; blooming spices in oil; mug cakes; sanitizing damp sponges.
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Save your recipes in Cooked.it, freeMore about microwave oven
An appliance using ~2.45 GHz non-ionizing electromagnetic waves (from a magnetron) to agitate polar molecules, chiefly water, generating heat inside food directly rather than through hot air.
A countertop metal box with a mesh-screened door (that mesh IS the shielding: holes smaller than the waves), rotating glass plate, and magnetron hidden behind the control panel.
Buying guidance
Inverter models (true variable power) melt and defrost dramatically better than duty-cycle units; 1000 to 1200W is the useful home range; sensor reheat is the feature that actually gets used.
Care and cleaning
Steam-clean trick: microwave a bowl of water + lemon 3 minutes, wipe; keep the door mesh and seals intact; never run empty.
What it works with
Safe vessels: glass, ceramic, microwave-rated plastics/silicone. Never: metal, foil, single-use takeout metallics, melamine. Eggs in shell: no.
Empty operation: no.
Safety
General kitchen safety tips. Always follow the manufacturer's instructions and current food safety guidance.
Steam burns on uncovering are the real everyday hazard; superheated water can flash-boil. Disturb with a utensil before removing; damaged door seals are the only radiation concern worth having (get dents serviced).
Substitutions
| Use instead | How much | What changes |
|---|---|---|
| Steamer basket on the stove | For vegetable steaming | Slower, one more pot |
| Double boiler | For melting chocolate | Gentler, more attention |
| Low oven + damp cover | For reheating | Better crusts, far slower |
Common mistakes
- Metal, sealed containers, and whole eggs (arcing and steam explosions).
- Superheating still water (add a chopstick or use marked vessels).
- Microwaving in takeout containers or cling wrap not rated microwave-safe.
- Expecting browning: microwaves don't do Maillard (that's the oven/pan handoff).
Product picks
- Inverter microwavesSee it on Amazon: inverter microwaves
- Microwave steamersSee it on Amazon: microwave steamers
- Splatter coversSee it on Amazon: splatter covers
History
In 1945, Raytheon engineer Percy Spencer stood near an active radar magnetron and noticed the chocolate bar (by most accounts a peanut cluster bar) in his pocket had melted; popcorn kernels confirmed the discovery, and the 1947 'Radarange' (six feet tall, water-cooled, restaurant-priced) commercialized it. Countertop models arrived in 1967, and by the 1980s the microwave had rewired home eating. Decades of 'radiation' anxiety followed a linguistic accident: microwaves are non-ionizing (radio-family) waves: the same physics as your Wi-Fi, at higher power and safely caged.
Myth or fact
- Common concern
- Persistent beliefs hold that microwaves 'destroy nutrients' and 'leak dangerous radiation.'
- What the evidence says
- Nutrition research consistently shows microwave cooking preserves water-soluble vitamins as well as or better than boiling/steaming on the stove: shorter times and less water mean less nutrient loss. On radiation: microwaves are non-ionizing (they jiggle molecules; they cannot alter DNA the way X-rays can), emissions are FDA-limited to trivial levels at the door, and the mesh screen blocks the waves by simple physics of wavelength.
- Practical takeaway
- A functioning microwave is one of the safest, most nutrient-friendly cooking tools in the kitchen. Respect steam, skip metal, replace a unit with a damaged door, and stop apologizing for 'nuking' vegetables done right.
Questions people ask
Do microwaves destroy nutrients in food?
No more than other cooking, usually less. Nutrient loss tracks heat, time, and water contact; microwaving is fast and nearly waterless, so steamed-in-microwave vegetables typically retain MORE vitamins than pot-boiled ones.
Is standing near a microwave dangerous?
No: emissions at the door are limited to levels far below harm, dropping further with distance, and the waves are non-ionizing (radio-family, not X-ray-family). The realistic hazards are steam and molten cheese.
Why can't metal go in the microwave?
Metal reflects microwaves and concentrates charge at edges and points, arcing sparks that can damage the magnetron or ignite. (The cavity walls are metal by design; the geometry is engineered; your fork isn't.)
Why does microwaved food heat unevenly?
Standing waves create hot/cold spots (the turntable's whole job), and dense or frozen regions absorb differently. Fixes: ring-shaped arrangement, center hollow, stir/flip halfway, lower power for longer.
What's actually the best thing to cook in a microwave?
Vegetables, seriously: damp, covered, 2 to 4 minutes = perfect steaming. Also elite: melting chocolate at 50% in bursts, softening brown sugar (damp paper towel), blooming spices in oil, reviving stale bread (briefly, damp-wrapped).
Why do microwaves say not to run empty?
With nothing to absorb them, the waves reflect back into the magnetron and cook the machine instead. Even reheating a dry bagel gives them somewhere to go.
Can I microwave water for tea?
Yes with one caution: ultra-still water in smooth vessels can superheat past boiling without bubbling, then erupt when disturbed. A wooden stir stick or teabag in during heating prevents it. (Kettle loyalists' real objection is temperature control, and they have a point for green tea.)
Trivia answer
In 1945, radar engineer Percy Spencer noticed the chocolate-peanut bar in his pocket had melted while he worked near an active magnetron, then popped corn kernels with it to confirm.
Origin and background
- Why it was developed
Accidental discovery during radar magnetron work; commercialized as the Radarange (1947).
- What it was first used for
Commercial/institutional rapid reheating (early units 6 ft, ~750 lbs, water-cooled).
- How the design changed
1967 countertop (Amana); turntables, inverter power control, sensor reheat, convection combos.
Then and now
- Original materials
Magnetron + shielded steel cavity: unchanged in principle.
- Uses today
Reheating, steaming, defrosting, precision melting, quick-prep assists.
- Modern alternatives
Steam ovens (gentler, slower), convection-microwave combos (adds browning).
Related
- Double boiler
- Steaming
- Convection oven
- Air fryer
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