In the pursuit of a cleaner and healthier planet, nanotechnology has emerged as a transformative force. Nanomaterials—particles thousands of times smaller than the width of a human hair—are increasingly being used to cleanse polluted water, soil, and air. These tiny materials offer remarkable capabilities, removing hazardous chemicals and heavy metals efficiently and often with minimal energy input. However, alongside these promising benefits lies a critical question: could these microscopic allies also pose hidden risks to human health and ecosystems?