U.S. stock indexes this morning were trading along the flatline and pared their steep losses after markets careened out of control in volatile trading overnight after a speech by U.S. President Elect Donald Trump helped reassure investors after his upset win vs. Hillary Clinton caught investors around the globe by surprise.

Right after the opening bell on Wall Street, the Dow Jones industrial was down only 30 points, or 0.2%, after tumbling as much as 800 points in late-night futures trading. The broad Standard & Poor's 500 stock index, which was down 5% overnight and hit a trading halt designed to limit losses, also so trimmed its steep declines and was down 0.3%.

"Risk aversion is likely to remain strong in the U.S. session today," says Craig Erlam, senior market analyst at OANDA, adding that he thinks "we may have seen the worst of the moves in the markets" following Trump's surprise win.

The key question now is how long the market shock will last?

Back in late June, the U.S. stock market suffered a two-day drop of 5.6% after the surprise Brexit vote in which Britain voted to exit the single-market European Union. The stock market, however, came to its senses and fully recoverd 10 trading days later.

The Trump-driven tumult, however, may keep the uncertainty level high in markets for a bit longer, says David Joy, chief market strategist at Ameriprise Financial.

"I think the environment will stay uncertain for awhile," Joy told USA TODAY, citing the shock factor of Trump's win and the many unknowns related to what's Trump policies will be and what the chances are of them being enacted by a GOP-controlled Senate and House of Representatives that are not great fans of the president-elect after a brusing presidential campaign.

"We will get through this but the adjustment process will take longer," says Joy.

World markets were very volatile through election night in the U.S., with stocks, currencies and bonds swinging wildly as investors factored in the reality that the Republican businessman could best Democrat Hillary Clinton in the 2016 presidential race. Trump, who has never held public office, defeated Clinton to be elected the 45th president of the United States on Wednesday. Wall Street had been pricing in a Clinton win.

Japan's Nikkei 225 plunged 5.4% to close at 16,251.54 while Hong Kong's Hang Seng index lost 2.2% to 22,415.19%. The Shanghai Composite index lost 0.6% to finish at 3,128.37. Futures on the Standard & Poors 500 index hit a trading halt designed to limit losses. Dow futures were down 2.1%, S&P 500 futures were 2.3% lower and Nasdaq futures lost 2.7% at around 6.30 a.m. ET.

European markets opened sharply lower before paring its losses. Germany’s DAX index was off around 1% after opening down nearly 3%. France's CAC 40 was in positive territory by 0.4% after an earlier decline of 1.5% and Britain's FTSE 100 dropped 0.3%.

Earlier Wednesday, the Dow Jones industrial average was down about 638 points, or 3.4%, in futures trading, leading to fears that if the Dow's losses stuck when regular trading resumes today, the point loss could top the 610-point Brexit drop back on June 24. The Dow's earlier level would also challenge the record one-day plunge of 777.68 points back on Sept. 29, 2008, during the financial crisis.

Kathleen Brooks, research director at Forex.com, said that Trump “definitely sounded more presidential than he has done at any stage during the election campaign” during his victory speech, in which he praised Clinton," the Associated Press reported.

"I pledge to be president for all Americans. We are going to rebuild our inner cities... We will rebuild our infrastructure, which will become second to none," Trump said in his relatively soft victory speech.

Investors rushed into perceived havens, such as gold, which is up $26.90 an ounce, or 2.1%, to $1,301.40

The Trump strength in this election is similar to what happened during the surprise Brexit vote, which was characterized by untrustworthy polls, rising populism and an angry electorate.