Before September 13, the night Jonathan Miller appeared on the reality show Shark Tank to pitch his year-old custom energy bar business, Element Bars, Inc., his Web site got about 200 unique visits a day. That night it racked up 25,000. The next day brought another 20,000. Less than two weeks later sales had soared from 1,000 bars a week to 10,000 bars, and Miller had hand-signed 1,500 notes apologizing for the backlog that had delayed deliveries.

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Miller, 29, says he was able to keep his cool because he’d pitched a business before—he won the Kellogg Cup, a business-plan competition at Northwestern University’s Kellogg School of Management, for a golf-related class project—and was prepared for the negotiations, which were edited down for TV from 90 minutes to 15. “I practiced ahead of time, knew all the facts about the company, and was passionate,” he says. “I thought about what type of offer I’d accept, what could be negotiated, and also what the sharks cared about and would accept.” The one point on which he was firm was that he wouldn’t give up a controlling stake in the company. “That was partly for business reasons and partly to keep myself motivated,” he says. He also realized he might have to raise more capital later on, so he couldn’t “give away the whole farm in one shot.”

Although he maintains he didn’t originally think of the energy bars as a business idea, Miller was no stranger to entrepreneurship. In 1999, as a sophomore, he got so fed up with the high cost of textbooks that he started getcheapbooks.com, an online price-comparison textbook shopping site geared toward college students. By 2005 he was earning enough from the site to quit his job at the consulting firm. But a year and a half later, price-comparison Web sites had proliferated and the site stopped being quite as profitable, so Miller decided to boost his business skills with an MBA from Kellogg.

When an order comes in, a recipe is generated by the computer system. Workers assemble the ingredients in a small area set apart from the rest of the factory. As many as possible are locally sourced, among them apple-juice-sweetened dried blueberries from Michigan and honey from Harvard, Illinois. Batches of dough for large orders are mixed in an industrial Hobart, and then each bar is formed by hand and pressed into an individual mold before baking. Only the wrapping process is fully automated at this point.