Did you
ever seen electrical wires during summer when it are loose and during winter
when it are shorter? Or rails splitted in way impossible to imagine?
It is due fact, that with
increase of the temperature there grows dimensions of the solids. It is called
thermal expansion. Not only wires changes its
dimensions due to temperature. Almost all bodies are subjected to that phenomena.
Even massive brigdes, so in their construction there must be taken to account
that in winter occurs contraction 
and expansion 
of its dimensions in the summer.
But, there exists some materials which decrease their dimensions during heating. Such phenomena is called negative thermal expansion.
One od them is cubic Zirconium Tungstate which contracts over temperature range of 2 to 1050K which is previously unprecedented. These materials have a wide range of potential using ex. in engineering, photonic, electronic or structural applications. It is even possible to create a material with zero expansion - by creation of the composite from materials with negative thermal expansion and with thermal expansion.