SEC chief Jay Clayton says he is nervously eyeing retail-driven euphoria in the stock market

• Chairman of the Securities and Exchange Commission Jay Clayton told CNBC on Thursday he's concerned about stock market euphoria stemming from retail investors.
• "When stocks run away... we do get concerned because it is a situation where professional investors understand this, I do worry that retail investors do not understand that trees don't grow to the sky," Clayton added.
• His concerns come as all three major indexes hovered around record highs on Friday.
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Chairman of the Securities and Exchange Commission Jay Clayton $4 he's concerned about stock market euphoria that's stemming from retail investors.

"We are in a situation where with mobile communications, access, and the like, there is a new paradigm. There are more retail investors participating in the market than ever before," Clayton said.

"One thing we don't regulate directly...is euphoria and we're seeing some euphoria here," he added.

His concerns echo those of $4, who said earlier this week he's also worried about retail investors driving the market to dizzying new heights. Both pointed to the$4. Airbnb, for example, leaped 115% on its first day of trading. On Friday, all three major indices hit all-time highs.

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"When stocks run away... we do get concerned because it is a situation where professional investors understand this. I do worry that retail investors do not understand that trees don't grow to the sky," Clayton added.

His interview comes as the $4resulting in a $65 million settlement, as well as a complaint from the Massachusetts securities regulator stating that the trading app encouraged inexperienced investors to execute frequent trades.