The latest sell-off has come as a second wave of cases forced more lockdowns in Europe, threatening the economic recovery and spooking investors around the world.
Does the latest twist herald the end of a bull run or the beginning of a shift toward long-neglected niches?
The S&P 500 dropped 3.5 percent on Thursday, the biggest single-day fall since June 11, as big tech companies weighed on it heavily.
Now that the stock market has largely shrugged off the coronavirus, start-ups are scrambling to go public.
The S&P 500 climbed back above where it began the year on the same day that economists said the United States fell into a recession in February.