The increasing consumption of products containing nanomaterials that can be currently observed and forecasts of new developments and applications fan the fear of individuals and organizations regarding new risks to health. Considering experiences gained from previous technology developments, such fears are not completely unfounded. But are they really justified? And is it justified, moreover, to speak of “nanotoxicology” as a new discipline? This Review seeks to cast light on the phenomena that may occur as nanoobjects interact with cells, tissues, and organisms. Furthermore, we will demonstrate that the many data made available on the biological effects of nanomaterials do not always come from studies that can be considered reliable. We will point out the aspect of reliability with specific examples from the literature and will not address specific (nano)materials. In particular, inadequate methods will be described together with recommendations how to avoid this in the future, thereby contributing to a sustainable improvement of the available data.