Borosilicate glass is a heat-resistant glass made by adding boron trioxide to the silica mix, giving it very low thermal expansion. It withstands rapid temperature changes without cracking, tolerates oven and microwave use, and resists chemical attack, making it the standard material for laboratory glassware and heatproof kitchenware sold under the Pyrex brand. In food laboratories it is used for beakers, flasks, and sample containers because it does not leach contaminants or react with acids and solvents. Domestic oven dishes in borosilicate glass allow cooks to see browning while benefiting from even heat transfer and easy cleaning.