Celebrity Chemistry Class
The Chemistry of Couples
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The Chemistry of Couples
By Tracy Pepey

Explosive, burning, gotta-have-you-now connections. Some couples have them, others not so much. What makes some of Hollywood's most prominent couples -- like Brangelina and TomKat -- work? We've got the good word from Chemistry.com's Dr. Helen Fisher, who helped us uncover why certain Tinseltown twosomes sizzle -- and why their hookups with past partners fizzled.

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