That reaction happened after the Dow dropped 504 points to close at 10,917, making it the biggest loss for the Dow since the September 11th attacks.
The NASDAQ fell 81 points to 2,179.
Analysts say even if you haven't heard of Lehman Brothers, AIG, Merrill Lynch or Washington Mutual, you will feel the fallout.
What does today's stock drop mean for your retirement mutual funds and 401 (k)?
If you own stock in the affected companies, you'll definitely get hurt. Even if you don't, the ongoing tumult is driving down the whole market.
However, most experts say even with Monday's steep drop-off, stocks give the best long-term return.
"We have this inherent bias for action this desire to do something when in reality sometimes the best action to take is to stay right where you are," said Stuart Ritter, financial planner, T. Rowe Price.
What about your ability to get a loan?
At a time when it's hard enough to get credit, Lehman's demise may aggravate matters. However, it may increase the odds of the Federal Reserve cutting interest rates.
Some may be wondering how safe their bank accounts are after the nosedive. However, Lehman and Merrill are investment banks, not commercial banks. The federal government says 98 percent of commercial banks have plenty of money.
There may be a silver lining in all of this. Financial experts say when the stock market is down, there are lots of buying opportunities for brave investors.
"This is the kind of environment that millionaires and billionaires are made out of," said Mesirow Financial Chief Economist Diane Swonk.
Analysts say the Wall Street meltdown will affect the rest of the economy because people will have less money to spend.
Oil prices dropped again on Monday because investors figure a slowing economy means less demand for fuel.