The US Department of Defense is funding research into "soft robotics", i.e., robots that can change shape drastically and rapidly to suit their environment:

The Phase I milestone is:

1. Demonstrate a ChemBot, approximately the size (but not necessarily the form-factor) of a regulation softball (i.e., 30 cm circumference; 10 cm diameter; 500 cm3 volume), that can:
a) travel a distance of 5 meters at a speed of 0.25 meters/minute;
b) achieve a 10-fold reduction in its largest dimension; and
c) traverse through a 1 cm opening of arbitrary geometry and reconstitute its original size and shape, in 15 seconds.

Not quite the T-1000 from Terminator 2, but getting there. (Via IPList.)