Rods' counterparts are cones, which are three-dimensional geometric shapes with a circular base and a pointed top. Cones are commonly found in nature, such as in pine trees, volcanoes, and ice cream cones. In mathematics, cones are used to represent the surface of a sphere or a cylinder. They can also be used to describe the shape of a variety of objects, including lenses, antennas, and even some types of musical instruments.