Bicyclic compounds are organic molecules that contain two interconnected rings of atoms. These rings can be made up of carbon atoms, other elements, or a combination of both. Bicyclic structures can be found in various natural and synthetic compounds, playing important roles in fields like medicinal chemistry and materials science. The two rings in bicyclic compounds can share one or more atoms, leading to different structural types, such as naphthalene or indole. The unique arrangements of atoms in these compounds often result in distinct chemical properties and reactivity, making them valuable in the development of pharmaceuticals and other chemical products.