According to Wikipedia:

* A [**glass**](https://en.wikipedia.org/wiki/Glass) is any "solid that possesses a non-crystalline (that is, amorphous) structure at the atomic scale and that exhibits a glass transition when heated towards the liquid state".

* A [**glass transition**](https://en.wikipedia.org/wiki/Glass_transition) is "the reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle 'glassy' state into a viscous or rubbery state as the temperature is increased."

It seems like most familiar non-crystalline solids (e.g. household plastics, [cheese](http://conservancy.umn.edu/handle/11299/50089)) become more ductile and less brittle when heated.  Does this mean these are all considered glasses?  What is an example of an amorphous solid that is *not* a glass?