great

Now imagine walking around with a prince albert made of a prince rupert

Mackeral,
This is similar to toughened glass where the glass is heated and cooled very quickly creating a very high tension outer skin. Now grab your drill and try to put a hole through the toughened glass - it'll shatter into a million pieces because you've broken the surface tension. Whatever you do, don't tap the edge of your frameless shower screen with something that's sharp and heavy.

I understand Bullet proof glass is more laminate and composite (i.e. think polycarbonatess)technology.

Choco, fabulous link. Thanks.