The present era is considered the nanotech age. Nanomaterials have gained a great deal of importance in the field of technology, engineering, and medicine progression because of their tunable, physical, chemical, and biological properties rather than their bulk counterparts. Nanomaterials are classified based on their size, shape, composition, origin, and toxicity. Due to the increasing utility and industrial applications of nanomaterials, it has become important to investigate nanomaterials' toxicity and environmental risks. In the present review, we have critically discussed the applications, behavior, and toxic impact on humans, animals, and the environment. Its fate and challenges and future requirements for the development and design of safe nanotechnology for sustainable development have been discussed.