Shattered Glass

Just a few days ago I was helping to clear the fridge and was asked to wash the detachable glass panel used to separate the vegetable and fruits drawers from the rest of the fridge. After washing one side of the glass, I turned it over while applying a little pressure on the glass. Suddenly the glass shattered to tiny pieces as fine as grains of sand in my hands. Wonder why this happened?

Anyone with the answers please feel free to post a comment. ^_^