Abstract: Apparatus that may be used as a skylight or window for allowing natural light to enter a building has light impeding regions (104) arranged in a planar configuration above one or more other light impeding regions (100) arranged in a lower plane so that the regions are spaced apart. The arrangement allows selective transmittance of natural light so that light incident from directly overhead is largely impeded, but light from other angles is largely unimpeded. This reduces the variation in light levels within building structures, reducing thermal loading problems. The apparatus may also be orientation independent.