Subway tiles have been popular since the early 1900s when used in New York subway stations. They are now commonly made of glass instead of ceramic, which provides richer colors and is impervious to water damage. Glass subway tiles are ideal for use in bathrooms, kitchens, and pools. They are often used as kitchen backsplashes to provide beauty and protection from water. Subway tiles come in various sizes, most popularly 3"x6", and should be at least 8mm thick for best color and strength.