A balloon is an inflatable flexible filled with air and also gas, such as helium, hydrogen, nitrous oxide or oxygen. Modern balloons can be made from materials such as latex rubber, polychloroprene, or a nylon fabric, while some early balloons were made of dried animal bladders . Latex rubber balloons may be used as inexpensive children's toys or decorations, while others are used for practical purposes such as meteorology, medical treatment, military defense, or transportation. A balloon's properties, including its low density and low cost, have led to a wide range of applications. The inventor of the natural latex rubber balloon, (the most common balloon) was Michael Faraday in 1824, via experiments with air and various gases.