At the centre of every pod is a heating element, usually referred to as a coil. This coil is made up of a metal wire coil or mesh that is surrounded by a cotton wick. As the pod is filled with e-liquid the cotton around the coil becomes saturated, so when the battery powers the coil, causing it to heat up, the e-liquid in the cotton is vapourised which results in a vapour that is then inhaled.