Nanoscale bioreactors are tiny, engineered environments where biochemical reactions take place at the nanoscale level. These bioreactors are designed to mimic the natural cellular environments, allowing for precise control over the conditions in which biological reactions occur. They are typically constructed using nanomaterials such as nanoparticles, nanotubes, and nanofibers, and can be used for various applications in biotechnology, medicine, and environmental science.