text: In a twisted nematic device ( still the most common liquid crystal device ) , the surface alignment directions at the two electrodes are perpendicular to each other , and so the molecules arrange themselves in a helical structure , or twist .
simplified: In a twisted nematic device ( still the most common liquid crystal device ) , the surface alignment directions at the two electrodes are perpendicular to each other . The molecules therefore arrange themselves in a helical structure , or twist .