If making ratatouille, choose the long, purple or lavender Chinese eggplant. It's sweeter and has fewer seeds than European varieties, and holds its shape when cooked.
Tender-fleshed black Japanese eggplant is best fried or sauteed. The bitter Thai eggplant comes in a range of shapes and colors, and has a biting crunch, making it ideal for pickling or adding raw to sauces.
The most common of all is the European eggplant—the large, purple type found in supermarkets. It's best for baking because its tough skin holds its shape well, while the flesh becomes soft and creamy.