Some exhibit a cholesteric phase in which the application of a pressed hand on a black surface shows temperature variations through color patterns.  
In the nematic phase of these substances, molecules have a preferred orientation while their positions are distributed at random.  Some exhibit a cholesteric phase in which the application of a pressed hand on a black surface shows temperature variations through color patterns.  For 10 points, identify these substances, used in the displays of watches and calculators.
In the nematic phase of these substances, molecules have a preferred orientation while their positions are distributed at random.  
liquid crystals