1. Tech trouble: Shares in tech companies tumbled on Wednesday as investors worried about increased scrutiny of the industry and potential new regulations.

The main source of consternation was a hearing on Capitol Hill, where Jack Dorsey of Twitter and Sheryl Sandberg of Facebook testified on their efforts to combat foreign influence in elections.

Shares in Twitter (TWTR) dropped 6%, and Facebook (FB) shed 2.3%. Google (GOOGL) owner Alphabet dropped 1%. The tech-heavy Nasdaq ended the trading session down 1.2%.

JD.com (JD), a Chinese tech firm listed in New York, dropped 10% following rape accusations against its founder and CEO Richard Liu. He has denied the allegations.

2. Emerging market turmoil: Chinese stocks are in a bear market. Turkey's currency has collapsed. South Africa has stumbled into a recession. But will the pain spread further?

Investors have focused their attention on a slide in emerging markets stocks that has pushed the the iShares MSCI Emerging Markets ETF near a 14-month low. The ETF has now lost over 11% in 2018.

Copper, another closely-watched barometer of economic strength, has lost one-fifth of its value since early June.

The storm rocking emerging markets has its origins in Washington. Vulnerable currencies plunged as the US Federal Reserve steadily raised interest rates. And President Donald Trump's trade crackdown added gasoline to the fire.

Investors worry that the pain could spread, infecting other emerging markets or even Wall Street. That's what happened two decades ago during the Asian financial crisis.

3. US tariffs looming: The public comment period on the latest round of US tariffs on China concludes Thursday, meaning the United States could impose tariffs on around $200 billion of Chinese goods as early as Friday.

That would amount to roughly half of all Chinese imports entering the country. Trump has already imposed 25% tariffs on $50 billion worth of Chinese goods — and Beijing has retaliated in kind.

China has pledged to push back against the United States if it moves forward with the new tariffs.

4. Global market overview: US stock futures were edging lower.

Major markets in Europe and Asia were down. The Dow Jones industrial average closed 0.1% higher on Wednesday, while the S&P 500 was down 0.3%.

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5. Earnings and economics: Barnes & Noble (BKS) and Lands' End (LE) will release earnings before the open. Broadcom (AVGO) and GameStop (GME) will follow after the close.

A new Nike (NKE) commercial featuring Colin Kaepernick will air during Thursday night's NFL opener between the Atlanta Falcons and the Philadelphia Eagles. The controversial campaign has sparked product boycotts and put the company's stock under pressure.

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6. Coming this week:

Thursday — Barnes & Noble (BKS), Broadcom (AVGO) and GameStop (GME) earnings; NFL regular season begins

Friday — Jobs report