Nanoscale particles are known to exhibit novel and unprecedented properties that make them different from their corresponding bulk materials. As our ability to control these properties is further advanced, a huge potential to create materials with novel properties and applications emerges. Although the technological and economic benefits of nanomaterials are indisputable, concerns have also been raised that nanoscale structuring of materials might also induce negative health effects. Unfortunately, such negative health effects cannot be deduced from the known toxicity of the corresponding macroscopic material. As a result, there is a major gap in the knowledge necessary for assessing their risk to human health.