Three-year-olds are in a period of rapid development of self-awareness and cognitive abilities. They need to discover the world around them through play and exploration, so play is their main activity. However, that doesn't mean they can't do some simple thinking exercises. For example, through interactive play, they can learn basic concepts such as categorization, counting, comparing sizes, as well as basic reasoning and solving of problems. These exercises can be done through toys, books and parent-child activities. In short, three-year-olds need to be play-oriented, but there are some basic thinking exercises that can be gained through play.