 macromolecular molecules. This classification of molecules is becoming more and more important. That's the plastics. They have a variety of melting points and they actually have softening temperatures where they don't melt but they soften like butter. This is a piece of a casting material for making braces. I'm going to put this in hot water for just a couple of minutes and it's softening. This water is about 90 degrees. It's not quite boiling. I can mold it into some shape and then let it cool and once it cools it's going to be very hard. Let me show you an application from the same piece of material. This is a brace splint for for fitting on a thumb. This was made to fit this hand and when you look at this it's not soft and pliable anymore. It's very very rigid but it's molded to fit my hand. This is a macromolecular compound.