Imagine a device smaller than your hand being able to disinfect water in just 20 minutes! Well, this device actually exists. Researchers at Stanford University and SLAC National Accelerator Laboratory have developed a tiny black rectangle that can be placed in water to kill bacteria and germs. The device looks very plain but is actually covered in nano-structured molybdenum disulfide. Molybdenum disulfide is a photocatalyst, which releases electrons that cause chemical reactions to take place in the water. The small black rectangle reacts with sunlight and water and forms hydrogen peroxide and other antibacterial chemicals. Despite being a disinfectant, it doesn't filter the water. Even so, this is a big technology advancement, and a huge step forward to providing clean water to the over 600 million people who don't have access to clean drinking water.