Atomizers and coils are used in tanks, each coil is fitted with at least a wrapped wire and a cotton wick, the cotton is to soak up and heat up e-liquid into a vapour.

There are MTL coils used for producing small clouds and greater throat hit, as well as sub-ohm coil for big clouds and increased flavour. 

Aspire Coils

Innokin Coils

Other Coils