Preheat the grill. Brush the slices of bread lightly with olive oil and place on a baking tray. Toast under the grill for about 3 minutes, making sure they don't burn. Rub each crostini with a garlic clove for flavour.
Place the tomatoes into a medium bowl and drizzle with olive oil. Season with salt and pepper.
Place the crostini on a serving tray. Top each one with a slice of mozzarella cheese, cover with a spoonful of tomatoes and garnish with fresh basil.