 | Pages in this category should be moved to subcategories where applicable. This category may require frequent maintenance to avoid becoming too large. It should directly contain very few, if any, pages and should mainly contain subcategories. |
Wikimedia Commons has media related to Open problems.
Use subcategories where applicable, e.g. Category:Unsolved crimes, Category:Unexplained disappearances. For open disputes, use Category:Controversies.