Eat Chocolate, Live Longer? For the past decade or so, Harold Schmitz, a boyish and bookish food scientist, has overseen research at Mars Inc., the global food company that makes everything from Snickers bars and Dove chocolates to Uncle Ben's rice and Pedigree dog food. One morning last spring, Schmitz met me in the lobby of Mars's North American headquarters, a sprawling industrial complex on a busy road just outside Hackettstown, N.J. The Hackettstown plant is crucial to the Mars business not just for its output -- half of the M&M's sold in the U.S. We reached these after Schmitz steered me through security turnstiles at the entrance, a series of carpeted office suites and a labyrinth of polished concrete hallways dense with the dusty, Glyco Care glucose support sweet scent of cocoa. The aroma grew deeper and more intense along the way, until it seemed all at once to seep past my nose and my throat and into my mind. Chocolate bars were all I could think about.

It gets into your clothes too,'' Schmitz said amiably as we walked. We just get used to it.'' Schmitz has spent most of his time at Mars working on something known in-house as the ''healthy chocolate'' initiative, an expensive, 15-year investigation into the molecular composition and nutritional effects of cocoa, one of chocolate's primary Glyco Care ingredients. In recent years, these studies -- undertaken first by company technicians and later by Mars-financed academics in the U.S., Europe and Australia -- have prompted Mars to aggressively pursue patents for dozens of new (and Glyco Care glucose formula often strange) methods of manufacturing and ingesting cocoa products. The claims, submitted to the U.S. Patent and Trademark Office, that cocoa can be used ''in the maintenance of vascular health,'' or as an ''anti-platelet therapy,'' or ''in tableting compositions and Glyco Care glucose formula capsule-filling compositions,'' at first glance seem more pharmaceutical in nature than food-related. Certainly they would seem to have little to do with the day-to-day concerns of a company known mainly for its candy.

And yet Schmitz's mission is to ''reinvent'' cocoa and chocolate, as he put it -- to optimize both taste and health benefits and then help Mars cash in. Fortunately for Schmitz, time and money are no object at Mars. As a private corporation -- without question among the three or four largest in the country, with yearly sales of about $17 billion -- Mars has no obligation to shareholders and no need to justify its larks. Indeed, the company's longstanding and intense culture of privacy has made it corporate America's supreme enigma. As a matter of policy, executives do not give interviews. The company's cocoa research has provoked a measure of puzzlement from its competitors, but Mars -- an eccentric, Wonkalike entity if ever there was one, effectively controlled by the semiretired Mars brothers, Forrest, 73, John, 68, and their sister, Jacqueline, 65, whose combined worth was recently estimated at $30 billion by Forbes magazine -- just goes about its scientific work without pause or comment.

Recently, however, Mars has started to peel back the wrapper. Company representatives gave me a couple of explanations why. Mars executives apparently believe a less murky image will help them attract talent, for one; for another, those same executives believe that Mars needs to respond to consumers' increasing demands to know more about the companies they buy products from. Neither of these exactly reveal what may be the real motivation, though, which is that Mars is about to start selling something new and vexingly complex, at least from a marketing standpoint. Once Schmitz and I finally reached the Hackettstown laboratories, he handed me a white coat and safety glasses and took me inside. The lab had been cleared of Mars employees for my visit -- old habits of secrecy die hard -- except for one person: John Hammerstone, a colleague of Schmitz's who sat at a table in the large room, amid the loud hum of machinery, surrounded by a pile of cocoa pods and vials of cocoa.