PG stands for Propylene-Glycol, one of the main components of e-liquids. It’s particularly responsible for exhaling flavors, but it produces little vapor, in comparison with other ingredients. It also creates a strong hit. Its use is today decreasing compared to the use of VG (Vegetable Glycerin), which produces more vapor and will be used with more flavors to compensate for a lesser PG content. PG is also used in the pharmaceutical industry, the food industry or the show-business: it’s used in night clubs to create artificial smoke.