The tanks house a coil with a cotton wick passed through the middle or wrapped around the outside of it. Electricity flows through the wire when the mod button is depressed. The wire resists the flow of the electricity and this resistance cause the wire to heat up. The cotton draws E Lliquid from the tank until it is saturated. The heat from the coil causes the E Liquid to evaporate. Drawing air with your mouth on the drip tip pulls air in through the tank’s air holes, over the coil and into your lungs.