You don't see a new kindof phase transition every day. The first evidence for the one to the new state of matter termed a supersolid emerged in 2004 when a wee can filled with with liquid helium and squeezed solid at 25 atmospheres was set twisting back and forth on a very thin and springy shaft. Below about 0.2 kelvin-- ,2 degree above absolute zero--the frequency of twisting shot up as though the can had lost mass. implying that some of the helium was not moving while the rest of it continued to twist back and forth-- through itself!
Some things are too simple to be readily understood, and in the very cold world of quantum solids , such things are the norm-if superfluid liquid helium flows without any resistance Why Not Supersolids ?.
Some doubted this was the supersolidity that had been bravely hypothesized in the 1960s (Science, 1 July 2005, p. 38) , but newly published work with a single crystal of the problematic stuff in a silicon can has reduced the uncertainty due to grain boundaries in the earlier work