Magnetic particle inspection is a way of checking for tiny cracks or defects in metal objects, like airplane parts or car engines.
Imagine you have a metal toy car and you want to check it for cracks. First, you pour some iron filings (tiny pieces of metal) on the car. Then, you take a magnet and hold it close to the car. The filings stick to the car wherever there is a crack or defect.
Now imagine doing that on a much larger scale with a real airplane part. Technicians clean the part, apply a special magnetizing current, and then sprinkle on tiny magnetic particles. Those particles will stick to any cracks or defects in the metal, and show up as bright lines under special lighting. That way, technicians can find and fix any problems before they become bigger issues.
It's like a treasure hunt for cracks!