This Research Front comprises papers that present research on the detection of nanoparticles in the environment. Overall, significant advances have been made recently to detect engineered nanoparticles (ENPs) in environmental samples and in toxicological media. Although measurements are still not routine, the papers show promising developments have been made that will allow us to have greater confidence in our measurements of ENP concentrations and size distributions, thus enabling environmental regulators to evaluate the presently missing, yet key component of environmental risk, i.e. exposure.