BY THE NUMBERS

U.S. stock futures were lower this morning, likely extending Monday's sharp losses at the open. The Dow and S&P 500 are at their lowest points of November, and the Nasdaq's Monday close was its lowest in nearly seven months. (CNBC)

* Cramer: The sell-off can't end until these 10 problems are fixed (CNBC)
* Once popular tech stocks like Facebook and Apple are now getting crushed: Here's what happened (CNBC)

Bitcoin dropped 15 percent today to its lowest level since September 30 of last year, according to data from CoinMarketCap.com. The drop brings bitcoin's total losses in seven days to roughly 30 percent. (CNBC)