This short and very simplified exposition of plastic theory shortly tells how and why AnyShape reacts the way it does when it is heated.
First of all, there are many different types of palstic. AnyShape belongs to the group of plastic denoted thermoplastic. What characterizes thermoplastic is that it is hard when cold and more or less soft/liquid when warm. Additionally, thermoplastic has a fantastic characteristic - It can be reheated and shaped again and again.
Before we start you should know what a molecule is and what a polymer is. A molecule is a composition of two or more atoms and a polymer is "merely" a lot of molecules that are stuck together like pearls on a string. The picture below shows a random polymer.
Plastic consists of many polymers that are tangled together in one big lump. It can be compared to a pot with cooked spaghetti, where every piece of spaghetti is a polymer.
AnyShape has different characteristics at different temperatures. These characteristics are determined by the structure of the polymer that AnyShape is made of.
At this temperature AnyShape becomes liquid, and it is in this stage you can shape AnyShape. In this stage, the molecules easily glide between each other. This stage can be compared to freshly cooked spaghetti that is still moist.
Between glass and melting temperatures AnyShape will be flexible and you will be able to bend and stretch it, but it will typically go back to the shape it had before you started bending it. This can be compared to spaghetti that has just been cooked, but is no longer moist and therefore sticks together.