Benchmark Capital is one of the most prominent venture capital firms in Silicon Valley that's invested in nearly every major tech company in the past decade. Twitter, Uber, Snapchat and Instagram are all companies they've put money into in recent years. But now Benchmark Capital is looking at a different industry for their latest investments: marijuana.

Benchmark recently announced a $8 million investment into Hound Labs, a start-up based in Oakland, California that's working on a device that will determine whether people are too high to drive. While this is just the latest investment, it's hardly the first. Peter Thiel, one of the co-founders of PayPal, has sent millions of dollars to Privateer Holdings, a Seattle-based private equity firm that invests money in cannabis research and products. The Los Angeles-based private equity firm MedMen has raised more than $80 million in the past year to invest in marijuana-related opportunities. Other companies, such as PotBot which helps connect users with their perfect cannabis strain, are courting tons of interest from venture capital firms as California heads closer to January 1st, when marijuana will become legal recreationally throughout the state.

The state of California alone is the sixth largest economy in the world. So while marijuana's been legal in Colorado, Oregon and Washington for a few years, the cannabis industry in those states is only a fraction of what it could be in California. Experts expect the marijuana industry to be worth $6.5 billion in California by 2020. 

Private equity firms have largely stayed away from marijuana investments for several reasons. One is morality clauses made with investors that prevent them from putting money into any "unsavory" endeavors. Another is the illegal status of cannabis at the federal level, and the possible legal challenges these companies would face. But with more and more states legalizing marijuana, a lot of investors believe the federal government will eventually relent and either remove it's illegal status or simply turn a blind eye.

So if you're a college student trying to become a Silicon Valley magnate, forget creating an app that helps you find your socks and start thinking up a program that helps people roll the perfect joint.