Market craziness: What you need to know

Markets around the world plunged Thursday after a sharp sell-off in Chinese stocks renewed fears about the health of the global economy.

To catch up on what happened overnight and why U.S. and global markets are so volatile right now, read the stories below:

* Our live blog with minute-by-minute coverage of market developments in Europe.

* The billionaire investor's warning that a Chinese currency devaluation was rocking the rest of the world added another dimension to the market's unease.

* Noted investor and newsletter writer Gartman said a bear market had "begun in earnest globally" amid the turmoil in China and declines in oil.

* Oil fell to 12-year lows, as geopolitical concerns were overwhelmed by the reality that the market is awash in excess supply.

* One of the most successful market strategists of recent years says the markets appear to be in "free fall."