The oldest known pieces of glass are similar in use and processing to gemstones, often cold rather than hot, and cut rather than melted. Artisans cut and polish glass and set it in jewelry. At some point, our distant ancestors discovered how to cast glass in molds to produce utensils. Before the art of glass blowing was popularized, craftsmen were able to make glass tiles, small mirrors, and many different types of vessels that could be used to store wine, perfumes, medicines, and other valuable substances.