Tree leaves, with over 60,000 species, are vital for the environment. They vary in shape, size, and color, aiding in photosynthesis, which converts sunlight, water, and CO2 into glucose and oxygen. Leaves have a protective cuticle, regulatory epidermis, photosynthetic mesophyll, and nutrient-transporting veins. They produce food, regulate water and temperature, purify air, and support ecosystems. Leaves are also used in medicine and crafts, underscoring their importance.