Tomatoes, potatoes and eggplants are part of the Solanaceae family, and chile peppers are part of the Capsicum family. All of these are called nightshade vegetables, but they are really fruits. In tomatoes and potatoes, eating the leaves and the roots will make you ill; symptoms and intensity vary according to the quantity ingested. Green potatoes can make you ill. Peppers and eggplants too should be ripe before you eat the fruit; ripening reduces the toxins. Nightshade is a folk name; its origins are murky, but seem to refer to the fact that eating too much of any of these vegetables can kill you.