While significant research efforts have broadened the understanding of toxicity of QDs, there are large discrepancies in the literature and questions still remains to be answered. Diversity of this class material as compared to normal chemical substances makes the assessment of their toxicity very challenging. As their toxicity may also be dynamic depending on the environmental factors such as pH level, light exposure and cell type, traditional methods of assessing toxicity of chemicals such as LD 50 are not applicable for QDs. Therefore, researchers are focusing on introducing novel approaches and adapting existing methods to include this unique class of materials.  Furthermore, novel strategies to engineer safer QDs are still under exploration by the scientific community. A recent novelty in the field is the discovery of carbon quantum dots , a new generation of optically-active nanoparticles potentially capable of replacing semiconductor QDs, but with the advantage of much lower toxicity.
For decades, as astronomers have imagined advanced extraterrestrial civilizations, they categorized such worlds by the amount of energy their inhabitants might conceivably be able to harness and use. They sorted the hypothetical worlds into three types according to a scheme named in 1964 for Soviet astronomer Nikolai Kardashev. A Type 1 civilization could manipulate all the energy resources of its home planet (a distant goal yet for Earth) and Type 2 all the energy in its star/planetary system . A super-advanced Type 3 civilization would command the energy of its whole home galaxy. The Kardashev Scale has since become a sort of gold standard for dreaming about possible civilizations beyond Earth.