designer's own words:At the moment that we suddenly switch off the light, people’s vision can not adjust with the darkness. It may cause danger while we are moving in case we have to go upstairs by step; this may cause the danger. This type of tile was created to shine in the darkness. So we can easily move everywhere unless in the dark environment because we can see the way to go by this dark shined tile. Moreover this shined tile can give you more special trick when you turn off the light; which is you can created a chosen nice words such as “good night” word by using this tile on the wall.