Joe Kennedy (Sr.) made a fortune on the stock market before he started running rum.
Legend has it that old Joe was having his shoes shined one week before the stock market crash of 1929. The shoeshine boy said to Joe "Hey, I've got a stock tip for ya..." Joe, being shocked that a 12 year old boy would think he knew so much about the stock market, looked around, and realized that uneducated people everywhere were investing in sectors they did not understand.
He pulled out all his money, just a few days before the market crashed.
This may or may not be a true story, but it certainly illustrates the market today.
We are ripe for a crash, because people are betting their investments on other people's research (e.g. Red Herring).
I know what Exelixis does, because I am a geneticist. You can find out what they do, if you just go to their homepage. But, you should try to understand the science before you buy the stock.