Quantum dots are man-made nanoscale crystals that exhibit unique optical and electronic properties, including the ability to transport electrons and emit light of various colors. They are a central topic in nanotechnology and materials science. Quantum dots are artificial nanostructures that can possess many varied properties, depending on their material and shape. Due to their particular electronic properties, they can be used as active materials in single-electron transistors. The properties of quantum dots are determined by various factors, including size, shape, composition, and structure, such as whether they are solid or hollow. Quantum dots can be made from a variety of materials such as zinc sulfide, lead sulfide, zinc selenide, cadmium selenide, or indium phosphide. Their small size allows for some quantum dots to be suspended in solution, which may lead to their use in inkjet printing and spin coating. Quantum dots have potential applications in a wide range of fields, including catalysis, electronics, photonics, information storage, imaging, medicine, and sensing. They enable researchers to study cell processes at the level of a single molecule and may be used to develop more personalized medicine approaches and to treat cancer and other diseases. Quantum dots can even be employed to transport treatment drugs in the body, delivering chemotherapy drugs directly to cancer cells while minimizing the harmful impact on surrounding healthy cells.