I came across this awesome youtube video by Alfred Leitner where he is showing some fascinating experiments involving supercooled liquid helium. Helium turns into a liquid when cooled to ultra-low temperatures (<-268 degrees C) but when it is cooled further to -270 degrees C it turns into what is called a superfluid. In this superfluid phase, it has zero viscosity and flows through extremely fine pores without any resistance. It climbs up glass walls and has zero entropy (perfect order) but what I find most fascinating is that heat travels like waves through this phase. It hits boundaries and gets reflected, just like sound or light do!