(Fortune Magazine) – Last year Nasdaq and the NYSE targeted European stock exchanges. Now? Deal fever has struck U.S. derivatives markets.

1 How many exchanges are in play? Four. Last fall the Chicago Mercantile Exchange bid for the Chicago Board of Trade. Then Jeff Sprecher (above) of the Intercontinental Exchange (ICE) swooped in with a higher offer. This spring Deutsche Börse paid $2.8 billion for the U.S.'s biggest options market, the International Securities Exchange, and Nasdaq approached the options-heavy Philadelphia Exchange. Now several players are eyeing the New York Mercantile Exchange.

2 Why the sudden interest in these niche markets? Shares of plain-vanilla stock exchanges have cooled off since the feeding frenzy of the past year. But futures and options markets are still booming, trading at an average of 74 times earnings. That's giving them currency to do deals.

3 What's so great about them? While Big Board stocks can be traded anywhere, from small exchanges to electronic networks, futures and options markets often have a monopoly on their products (corn futures, for one, are traded only on the CBOT). These niches pay off: CBOT's 2006 pretax margin was 47%, to Nasdaq's 12%.

4 So will they all be bought? Some, like Philly, may survive if their big investors won't sell (Citadel, Morgan Stanley, and other investors own 45% of the PHLX). But the rest only become more appealing.