WO3, or tungsten trioxide, is a chemical compound made up of tungsten and oxygen. It appears as a yellow or blue powder and is known for its unique properties, including its ability to change color when exposed to different conditions. This makes it useful in various applications, such as in smart windows and sensors. In addition to its optical properties, WO3 is also used in catalysis and as a pigment in ceramics and paints. Its stability and resistance to heat make it suitable for high-temperature applications, contributing to advancements in materials science and technology.