Chemical substances may be combined or converted to others by means of chemical reactions. Forms of energy, such as light and heat, are not matter, and are thus not substances in this regard.
Halophiles are organisms that thrive in high salt concentrations. They are a type of extremophile organism. The name comes from the Greek word for salt-loving. While most halophiles are classified into the Archaea domain, there are also bacterial halophiles and some eukaryota, such as the alga Dunaliella salina or fungus Wallemia ichthyophaga. Some well-known species give off a red color from carotenoid compounds, notably bacteriorhodopsin.
Halo is the name for a family of optical phenomena produced by light interacting with ice crystals suspended in the atmosphere. Halos can have many forms, ranging from colored or white rings to arcs and spots in the sky. Many of these are near the Sun or Moon, but others occur elsewhere or even in the opposite part of the sky. Among the best known halo types are the circular halo, light pillars and sun dogs, but there are many more; some of them fairly common, others rare. The ice crystals respo