“Play in” is a playable facility for children to play. Different from normal facilities in playgrounds which children can only play with, “Play in” brings new possibilities for children to build and play with their imagination. The facility contain two main part, basic frame and assembled elements. The general structure is decided by basic frame. Children can build and play with assembled elements based on the basic frame. Because the flexibility of “Play in”, children from different areas, culture background and countries, would play in different way and invent their own way of playing.