Nanotechnologies and nanoscience have generated an unprecedented global research and development race involving dozens of countries. The understanding of associated environmental, ethical, and societal implications lags far behind the science and technology. Consequently, it is critical to consider both what is known and what is unknown to offer a kernel that future work can be added to. The challenges presented by nanotechnologies are discussed. Some initial solutions such as self-regulation and borrowing techniques and tools from other fields are accompanied by (...) a call for further research. (shrink)