CuO, or copper(II) oxide, is a black solid compound made up of copper and oxygen. It is commonly used in various applications, including as a pigment in ceramics and glass, and as a catalyst in chemical reactions. CuO can be produced by heating copper in the presence of oxygen or by thermal decomposition of copper(II) hydroxide. In addition to its industrial uses, CuO is also studied for its potential in electronics and energy storage. It has semiconductor properties, making it useful in devices like solar cells and sensors. However, CuO can be toxic if ingested or inhaled, so safety precautions are important when handling it.