Botanically a fruit, and by cultivation and use a vegetable, the tomato is native to South America, where it grew wild for many years, unnoticed except as a weed. Later discovered by the Spaniards in Montezuma's garden, it was taken back to Europe, and eventually appreciated for all its versatility and beauty.

Buying/storing tips:
This is the top-priority vegetable to grow yourself, because tomatoes are best when ripened right on the vine. Vine-ripened tomatoes grown outdoors in sunlight are twice as rich in Vitamin C as their greenhouse counterparts. There are many, many varieties of tomatoes available these days, in many sizes, shapes, and colors.

I like to use them fresh only when in season, and would prefer to use a good brand of canned tomatoes rather than hothouse-bred tomatoes off-season. If you have room in your freezer, you can successfully freeze ripe whole tomatoes in sealed plastic bags. When you defrost them, the skins pop right off and the tomatoes are ready to become soup or sauce just like that.

When buying tomatoes, choose firm, plump ones with a good fragrance. Avoid soft, dented, or overripe tomatoes, or those that are hard or pale (unless they are a light-colored heirloom variety). If you do end up buying underripe tomatoes, store them at room temperature out of direct sunlight in a brown paper bag. Or find a good recipe using green tomatoes. (See Fried Green Tomato Pillows, Fried Green Tomatoes, Tomato Chutney, Tomato Jam.)

Culinarily Speaking:
I have very few iron-clad cooking rules, but here's one I think few people would argue with: Vine-ripened tomatoes in season should be tampered with as little as possible. After all, who are we mortals to think we can improve upon perfection itself?

Nutritionally Speaking:
Tomatoes have a high Vitamin C content and are a good source of the antioxidant lycopene.

Recommended Reading:
The very best book I have ever seen on the subject of tomatoes is the brilliant, "The Good Cook's Book of Tomatoes," by Michele Anna Jordan (published by Addison Wesley and distributed by HarperCollins). It makes for wonderful reading, is very informative and entertaining, and has great recipes. Find it!