Plasma is luminous and can produce a glowing discharge. The glow is generated by the excited electrons moving around in the chamber, colliding with each other and creating photons, particles that transmit light. The light given off by the plasma is a result of an interaction between a cathode and an anode, generating the complex circuit to produce the glow. A low pressure environment is needed to produce the glow, along with the right combination of gases. Argon and oxygen are typically the most popular.