Those pictures you see of shattering roses are roses dipped in liquid air or liquid nitrogen. Materials such as iron and plastics also temporarily become brittle after being dipped into liquid air, but copper and brass become tougher. Exposure to liquid air increases the strength of certain types of magnets and make metals conduct electricity better.
Air becomes liquid at about minus 190 degrees Celsius. It is so cold that it boils when poured over ice.
Liquid air looks like water with a bluish tint.