At Harvard University, researchers were able to slow light to 20 km/h. Moreover, they went ahead and decided to completely stop the light. The basis of the experiment is a supercooled material known as Bose-Einstein. This condensate is formed at a temperature of only a few billionths of a degree above absolute zero, the atoms therefore have very little energy to move. Keep in mind that the absolute zero is an abstract concept that cannot be achieved.
It was the first time a light was completely stopped.