Hydrogen stocks are companies involved in hydrogen production. These chemical producers have found a new market in recent years as hydrogen fuel cells have emerged as an important facet of the clean energy boom. Hydrogen is commonly used in fuel cells as a means of generating gas and heat, but it is also used in the processes of refining petroleum and creating fertilizer. Investors seeking exposure to this versatile chemical can gain it through funds such as the Global X Hydrogen ETF. A few of the most popular hydrogen stocks are Plug Power and Bloom Energy.