Attention all chocoholics! Here's a way to satiate your sweet tooth without gaining a single gram. In fact you're likely to work off plenty of calories as you explore "Chocolate: The Exhibition."

This major show, which opens Nov. 3 at the National Museum of Nature and Science in Tokyo's Ueno Park and was originally held at Chicago's Field Museum, is much more than just a paean to the world's favorite candy. It's an opportunity to find out all about its history, how it is produced, and how it gets from the tree to your chocolate bar (and your waistline).

Once you have entered, via a gate made of chocolate shaped to evoke the museum building itself — though how they stop it from melting under the heat of the spotlights is a mystery worthy of a lost civilization — the exhibition unfolds through a series of different themed "zones" that take you from seed to sweet.