The morphology of a liquid-crystalline ABA triblock copolymer with polystyrene (PS) blocks (12 vol %) and a side chain nematic liquid crystalline B block has been studied by TEM and temperature dependent SAXS measurements. Above the clearing temperature (T-c = 122 degrees C) the morphology is characterized by a body-centered cubic (bcc) lattice of polystyrene spheres. The transition to the nematic phase induces a reversible transition to a morphology of hexagonally packed cylinders by coalescence of the PS spheres along the [1,1,1] direction of the bcc lattice.