Investors have pushed stocks to overvalued levels in several sectors of the market, says CNBC's Jim Cramer.

Many of the sectors include young, unproven companies.

"In other words, there's bubbling everywhere, and it does worry me," Cramer said. "We saw too much cloud. We saw too much organic food. And now I think we're getting too much of a whole set of areas . . . , [such as] 3-D printers."

Editor's Note: Stocks to Drop 90%? These 5 Charts Reveal Why . . .

Among the companies Cramer mentioned were Violin Memory, which makes flash storage drives; Voxeljet, which makes three-dimensional printers; Sprouts Farmers Market, a natural food store; and The Fresh Market, a specialty foods store.

Violin Memory has plunged 58 percent since its Sept. 27 initial public offering and Voxeljet, which went public last month, has plummeted 46 percent since Monday.

As for Sprouts, which went public in August, it has dropped 23 percent since Oct. 21, and The Fresh Market has lost 28 percent since Aug. 9.

In another possible indication of market mania, Snapchat, a message service that doesn't even have revenue yet, turned down a $3 billion acquisition offer from Facebook, The Wall Street Journal reported last week.

Robert Cryan of Breakingviews sees that offer as an indication of Facebook's weakness.
"The social network paid $1 billion for no-revenue Instagram a little over a year ago," he writes.

"Now, it’s said to be dangling as much as $3 billion to lure a mobile app that sends self-destructing digital images. Facebook’s apparently escalating need to buy off marauders at its moat suggests its defenses may be scalable."

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