Light micrographs of skeletal muscle fibres stained with haematoxylin eosin (left) and under polarised light (right). With haematoxylin and eosin the cross striation with alternating dark and light bands can be seen. The dark bands are called A bands because they are anisotropic and glow with the polarised light. The light bands seen with the haematoxylin and eosin are called I bands because they are isotropic and do not shine with the polarised light.