If you break glass, it's often not enough to just sweep up the area. If you do this, you often leave behind very small slivers of glass that are just waiting to embed themselves in your foot. To clean up those very little slivers of glass, I find that a piece of bread (yes, that's not a typo) works really well. Wipe the entire area where there was glass with the piece of bread. The very tiny slivers of glass embed themselves in the bread instead of your foot and it is then safe to walk in the area.