There have been plenty of tries at shape-changing materials, but this one might be the most practical yet. The University of Rochester has created a polymer that returns to its original shape when subjected to body heat -- touch a curled mess of the stuff and it straightens out. The solution was to attach polymer strands using molecular links that inhibit crystallization, which prevents the polymer from returning back to its original shape. When you tweak the number and substances of the links, you can customize the temperature where that reversion happens (in this case, just below normal body temperature).
That's a fun trick in itself, but the kicker is that the material also stores vast amounts of elastic energy. It can lift something a thousand times its weight -- a thin wire could pull a big toy car, for instance.
If the polymer is put into use, that force could come in handy. The University envisions clothes that automatically fit themselves, and it could also lead to artificial skin and sutures that tighten up on their own. Any such products would likely be years away, but the days of unintentionally baggy shirts might just be numbered.