Lighting has been a central concern in architecture and design since ancient times. While the use of natural light has always been an aspect of architectural practice, for thousands of years buildings considered the effects and uses of early forms of artificial lighting, such as candles, rushlights, and oil lamps. Developments in lighting saw rapid changes during the Industrial Revolution. Gas street lamps arrived in London in 1815; the electric arc lamp, made from two carbon electrodes, was developed in the early 19th century and first used at the Paris Opéra in 1844; and the Englishman Joseph Swan and American Thomas Edison developed the first incandescent electric lamps in 1878 and 1879, hugely increasing access to electrical lighting. Iconic lamp designs, such as those by Tiffany Studios and Isamu Noguchi, have become iconic, historical works. In the mid-20th century, fluorescent lighting was widely installed in offices and schools. In recent decades, energy conservation has been a major concern, leading to the continued development of more efficient technologies and designs.