As is always the case with dichotomies, unsupervised learning encompasses all that is not supervised. We are here in the opposite situation—we just have a set of variables with no response. A quite famous example here is when a child is given some wooden toys of different shapes and is asked to separate them into two groups. This child has no rule or expected output, just the request to create two separate groups. He will have to sort out some kind of rule on his own. This will probably involve looking at the color, the shape, or the dimensions.