Biology is complex. We need models to make it simpler. We can test anti-cancer drugs on tumor cell cultures, but they are anything like a “real” tumor: that resembles an “ecosystem”, where multiple cell populations coexist and interact with each other. In a paper published on Cell, scientists managed to bring that complexity…on a chip! Not only they reproduced the 3D micro-architecture of the tumor microenvironment, but they also characterize the response to an immunomodulatory drug.