In the late 19th century, Otto Schott discovered that adding boron to glass batch -- creating what came to be known as borosilicate glass -- changed the properties of the glass in several important ways.
Compared to "plain" soda-lime glass, borosilicate glass has a greater resistance to chemicals and a much lower coefficient of expansion (by about 70%). The lower COE makes the glass more resistant to thermal shock and therefore more suitable for cookware and laboratory equipment.
Borosilicate glass is best known under the commercial names Pyrex (Corning trademark) and Kimax (Kimble/Kontes trademark). It is often referred to by artists as "boro" and is popular among some lampworkers and glassblowers.