Cellulose nanocrystal suspensions in apolar solvent spontaneously form iridescent liquid crystalline phases but the control of their macroscopic order is usually poor. The use of electric fields can provide control on the cholesteric orientation and its periodicity, allowing macroscopic sample homogeneity and dynamical tuning of their iridescent hues, and is demonstrated here.The authors acknowledge funding by the French National Research Agency under grant agreement ANR-08-NANO-P235-36 and B.F-P. acknowledges the Travel Grant COST-STSM-FP1205-30247
