Heat resistant to approximately 500 degrees Fahrenheit, Pyrex glass is safe to use in an oven or a microwave. Originally made from borosilicate glass, Pyrex glass was first marketed in 1915 by Corning Incorporated, which first used this type of glass in 1912 for railroad signal lanterns. The glass was adapted to create a baking tray for use in ovens in 1915.Today, Pyrex glass is made from borosilicate glass and soda lime glass, and is used in applications such as industry, laboratory, and kitchen.