This is a very large and diverse genus of plants. It includes annuals, herbaceous perennials, vines, shrubs and small trees. Taxonomists are always at work debating about which species belong in each genus. That is why it can only be estimated that there are between 1,500 and 2,000 species in this genus.

At one time in history, people thought that all of these plants were poisonous. Some of them are but many like tomatoes and potatoes contribute greatly to the average diet of many people today.