**1. What is a Tetrad?** |

**2. What is the intention of this website?** |

**3. Who published the first Tetrads?** |

**4. Was the problem already known before 1975?** |

**5. Is it easy to find a tetrad with hole?** |

**6. Can a schoolkid find a tetrad with no hole?** |

**7. What is the benefit of polyomino tetrads?** |

**8. Why was the order-11 polyomino tetrad not found earlier?** |

**9. Which tetrads are shown in Gardner's book?** |

**10. Can the outline of a Tetrad form a regular polygon?** |

**11. Can two tiles of a Tetrad form a regular polygon?** |

**12. What about circles and tetrads?** |

**13. Can four quadrilaterals form a tetrad?** |

**14. Can four pentagons form a tetrad?** |

**15. Which tetrads can be made with hexagons?** |

**16. Are there tetrads with no common vertices?** |

**17. Can two tiles surround the others? New 2020-02-20** |

**Planned: Are convex tiles possible?** |

**Planned: Are convex tetrads possible?** |

**Planned: What about symmetric tiles?** |

**Planned: Which symmetric tetrads are there?** |

**References - Where can I read more about tetrads?** |

**Comments - What do experts say?** |