Billionaire inventors

"To invent, you need a good imagination and a pile of junk." So said Thomas Edison, inventor of so many things we take for granted today and the archetypical American entrepreneur-inventor.

Edison became a rich man thanks to his imagination's ability to transform "piles of junk" into products and businesses that didn't previously exist. Today's more knowledge-based world may demand less physical junk and more service ideas as invention's starting point, but these 10 billionaire inventors are worthy heirs to Edison's tradition.

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Only five of our list are Americans; there is no national patent on inventiveness. Others come from as far a field as Thailand and Germany. But America provides more fruitful soil than most places for nursing a smart, original idea into a fortune.

There is little else that unites them, beyond having had an odd idea that in retrospect seems so simple and obvious, provoking the universal reaction, "Why on earth didn't I think of that?"

Take Brad Hughes: The former real estate executive thought of putting up a bunch of lockers off a highway somewhere, where people could keep stuff. Hughes Public Storage is now the largest self-storage company in the U.S. and has made Hughes a fortune we value at $5.3 billion.

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Or Jeff Bezos: He dreamed up the ides of selling books over the Internet. Cutting out the need for inventory, as well as the tactile but costly pleasure (for a bookseller) of browsing the aisles, cut costs so Bezos could sell at a discount. Turned out that bookworms were as price-conscious and lazy as the next person and more than happy to order from their computer. The $4.4 billion fortune Bezos made from Amazon.com lets him now pursue his passion for space travel.

Bezos solved a problem many didn't know they had. Michele Ferrero, matriarch of the family that is one of Europe's largest chocolate makers, also solved an unrealized problem--the lack of a spreadable breakfast chocolate. Combining chocolate and hazelnuts proved to be the answer. Nutella has joined a roster of Ferrero brands, including Ferrero Rocher, Tic Tac and Kinder Eggs, that is the basis of the family's $10 billion fortune.

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On the other hand, James Dyson, the eponymous inventor of the yellow and transparent vacuum cleaner, was seeking to solve a well-known problem: the fuller a vacuum cleaner got, the less efficiently it worked as the bag containing the sucked-up dirt obstructed the suction.

Dyson, a Brit who had gone to art school to study design and engineering, ran through 5,127 prototypes until he perfected an upright vacuum that used spinning technology to maintain constant suction. He introduced his vacuum in the U.K. in 1993, and it was an immediate hit, setting him on the way to a $1.6 billion fortune.

The inventor has announced plans to open the Dyson School of Design & Innovation in 2008. Perhaps it should put over its door some other words from Thomas Edison: "Opportunity is missed by most people because it comes dressed in overalls and looks like work."