Wash tomatoes and basil. Core tomatoes and cut into thin-to-medium slices. Slice mozzarella into thin slices (you can make them thicker, it just depends upon your taste). Place a single layer of basil on four plates (3-4 leaves each); then layer tomato slices on top of the basil (3-4 slices per plate). Top each slice of tomato with mozzarella. Drizzle one-half tablespoon of olive oil and one-quarter tablespoon of balsamic vinegar over each dish, and lightly season with salt and freshly ground pepper. Cover and refrigerate for 15-30 minutes before serving.