This classic salad from the island of Capri, just off Italy's southern coast near Naples, relies on just four perfect ingredients: vine-ripened tomatoes, fresh mozzarella, bright green basil and fruity olive oil. Use only the very ripest tomatoes, as their juices mix with the olive oil to make the dressing. It is important that the oil be of the highest quality, because the difference between an average and a superior one will be evident here.One of Italy's best-known cheeses, fresh mozzarella is soft and spongy textured. It is sold packed in liquid at well-stocked supermarkets, cheese stores and Italian groceries. Fresh mozzarella was traditionally made from the milk of the water buffalo, but cow's milk is used elsewhere and increasingly in Italy, as well.