Movie S3.

The aligned active nematic direction is in situ rotated. The aligned active nematic spontaneously transits from laminar to turbulent flow upon melting 8CB into the nematic phase at 36 °C. We subsequently rotate the magnetic field by 90°, and reverse the phase transition back into the smectic-A phase. The active nematic reestablishes the aligned state following the new easy axis, at 90° from the initial configuration.