Some materials can carry electricity perfectly, with no energy lost. These are called superconductors, but the ones we know only work when they are made very, very cold. In 2023, a team in South Korea said they had made a material called LK-99 that did this at normal room temperature. That would be a huge deal.
The news spread fast, especially because of a video showing a piece of the material tilting up off a magnet. Scientists all over the world tried to make LK-99 and test it themselves. Almost none of them could get it to work as a superconductor. They found the tilting in the video came from ordinary magnetism, and a strange reading came from a bit of impurity in the material.
In the end, scientists decided LK-99 was not a room-temperature superconductor. A big surprising claim needs strong proof, and one exciting video is not enough.