Colloidal nanoparticles are tiny particles that range in size from 1 to 100 nanometers and are suspended in a liquid medium. These particles can be made from various materials, including metals like gold and silver, or semiconductors like cadmium selenide. Their small size gives them unique properties, such as increased reactivity and enhanced optical characteristics. These nanoparticles are used in various applications, including medicine for targeted drug delivery, electronics for improving device performance, and environmental science for water purification. Their ability to interact at the molecular level makes them valuable in advancing technology and improving health outcomes.