The incandescent lamp was invented by Thomas Edison in 1879. At that time, filaments were carbonized fibers made by smothering a certain type of bamboo grown in Kyoto, Japan, but these days a variety of materials and methods are introduced to produce light bulbs. There are many types of light bulbs, each with their own purpose. For example, there are silica bulbs with silica particles coated electrostatically on their inner surface to vastly improve light transmission and diffusion, krypton bulbs injected with krypton gas (higher atomic weight than the normally used argon gas) to increase brightness, and reflector lamps using highly reflective aluminum on their inner surface.