If you see the photos in the video above in colour, you should know that they are actually black and white. This is an optical illusion created by artist and developer Øyvind Kolås.How does it work?To create this optical effect, Øyvind Kolås placed colour dots over a black and white image. He explains that these points of saturated colour, superimposed on a black and white image, have a totally different meaning for the brain: it sees the photo in colour. This technique is named "colour assimilation grid illusion".Why does our brain see colour?According to Sydney University scientist Dr Bart Anderson, a vision specialist, our brain compresses visual information so that it can be interpreted quickly.An even more effective methodIf you're already impressed by these results, Øyvind Kolås also demonstrated that this technique works even better when you use a colour grid with parallel lines.An illusion that applies to videoMoreover, this optical illusion isn't restricted to photos. Using the same coloured grid technique, you can do this with videos as well, and the results are amazing.Our brains like it!Our brain is a complex and intriguing machine, especially in the presence of optical illusion. In a BBC television report, another technique was used to see a picture in colour, when it was actually black and white. The technique consisted of staring at a dot on an image containing false colour for about ten seconds, then looking at the black and white picture again. And like magic, our brain recreates all the colours of the image. Amazing!