When light travels from the sun to the earth, the medium in which it travels is mostly empty space. When light travels through an optical tool the principal media are air, glass and then air again before the light hits the eye. Glass can, depending on its shape, thickness, and index of refraction transmit light in a totally different direction than it had entered, a principle that is used in these building blocks. These objects are carefully designed to allow natural light to flow into windowless spaces.
Building blocks change direction of light
Glass is a useful and versatile material, unbeatable when there is a need to force light to go around the corner. Imagine bringing natural day-light to windowless rooms, for ever. The beauty of it is that by turning the blocks, 90 or 180 degrees the light will go this, or that, direction. Same principle at work as described in the other articles here about optical phenomena in architecture. Vary the thickness of the glass, et voilà!