CNBC.com's Pippa Stevens brings you the day's top business news headlines. On today's show, CNBC's Kristina Partsinevelos recaps Cathie Wood's response to Wall Street shorting her ARK Innovation Fund. Plus, Robinhood posts a strong quarter in its first earnings report as a public company—but warns that trading on the app is slowing down.

Cathie Wood says stocks are not in a bubble, thinks investors betting against her fund are off base

ARK Invest's Cathie Wood on Thursday defended her innovation-focused strategies in the wake of investors betting against her funds.

"I don't think we're in a bubble which is what I think many bears think we are," Wood said Thursday on CNBC's "Tech Check." "In a bubble, and I remember the late '90s, our strategies would have been cheered on. You remember the leap frogging of analysts making estimates one higher than the other, price targets one higher than the other. We have nothing like that right now. In fact, you see a lot of IPOs or [special purpose acquisition companies] coming out and falling to earth. We couldn't be further away from a bubble."

On Monday, regulatory filings spotted by CNBC Pro showed Michael Burry bet against Woods' Ark Innovation ETF using options. Burry's Scion Asset Management bought 2,355 put contracts against the red-hot tech ETF during the second quarter and held them through the end of the period. Burry was one of the first investors to call and profit from the subprime mortgage crisis.

Other hedge funds also have put bets and other short bets against the firm's ETFs.

Robinhood revenue doubles last quarter, but stock drops 8% after app warns trading is slowing

Robinhood's revenue more than doubled in the second quarter to $565 million, bolstered by a massive surge in crypto trading, the stock trading app said in its first earnings report as a public company on Wednesday.

But the shares dove in after the company warned a slowdown in trading activity would hit revenues in the current quarter. Investors may also be concerned whether volatile crypto can continue to provide such a tailwind. Robinhood was last down more than 8%.

Revenue surged more than 131% in the period from $244 million a year ago and was near the high range of the company's forecast of $546 million to $574 million.

Amazon is reportedly planning to open department stores, its latest experiment in physical retail

Amazon is planning to open large retail locations that resemble department stores, The Wall Street Journal reported.

The newspaper, citing people familiar with the plans, reported that some of the first Amazon department stores are expected to be in California and Ohio. The locations will take up roughly 30,000 square feet, around the size of a Kohl's or T.J. Maxx store but only about the third of a size of a traditional department store.

The move would mark Amazon's latest experiment with physical retail stores after stealing market share in the retail landscape from incumbents with its e-commerce business. The company recently overtook Walmart as the world's largest retail seller outside of China.

The news had a ripple effect across the retail industry, particularly hitting the stocks of big-box rivals. Target, Bed Bath & Beyond and Best Buy shares fell roughly 1.5% in premarket trading, while Walmart shares were down about 1%.