In an interview with Bloomberg Television’s “Wall Street Week,” Jeremy Grantham proclaims that while Tesla has done extremely well, it is a bubble. The co-founder of GMO and value investing giant says that the EV darling is many multiples of the price to sales ratios that they were at this stage in their life, and that what they’re portending is that they will be as successful as the FAANGs of capitalism.

But Tesla could prove to be a crucial fork in the road, given their place in the fight against climate change and their potential to bring real, disruptive change. However, now that most other auto companies have jumped on the EV bandwagon, they are facing major competition as they move into their “phase two” and try to sustain their initial gargantuan success. “To live up to the expectation of the prize,” Grantham says, “will be impossible.”

In addition, many things could go wrong with Tesla, in particular with battery technology and production. The issue with Tesla’s bubble, Grantham told Bloomberg, is the same as other bubbles throughout history: that no one believes it will break or that prices will decline. But now, there are more people than ever buying into the idea that the bubble will never burst, so that when it does it has the potential to be the biggest break in U.S. history. But “if you can handle going short, getting out of the way, yes you can make a lot of money,” Grantham told Bloomberg when asked about when to pull out before a bubble bursts.

With this current bull market, inflation was ignored as the Fed poured money into the economy, making it different than every bull market that came before. “We’ve never seen anything like this,” Grantham contends. He added that the Fed has rattled the economy by encouraging dangerous asset bubbles over the years and that the central bank has not learned from its mistakes. Case in point: the meme stock craze, which Grantham portends is “worse than anything leading up to the 1929 crash.”