You may already have some reasons for wanting to invest in marijuana stocks, but as a refresher, here are some big reasons why investors are warming up to the marijuana market.

• 16 states have approved recreational marijuana laws.
• 36 states have approved medical marijuana laws.
• The legal marijuana market grew 17% in 2015 to $5.4 billion, according to ArcView Market Research.
• ArcView estimates the market grew another 25% in 2016 to $6.7 billion.
• Since recreational marijuana laws passed in 2012, Colorado's marijuana sales are already eclipsing $1 billion per year.
• Research into marijuana-based medicine suggests it could offer new hope to people suffering from devastating diseases, such as epilepsy.

The marijuana market is expanding quickly as states pass pro-pot legislation. But sales of marijuana could really take off now that voters have given marijuana proposals the green light in heavily populated states like California. California was at the forefront of the medical marijuana movement in the mid-90s, and as many as 1,000 medical marijuana dispensaries already operate there.