A quantum dot is a nanocrystal made of semiconductor materials that are small enough to exhibit quantum mechanical properties. These are very, very tiny particules on the order of a nanometer in size composing hundred to a thousand atoms. These semiconductor materials can be made from an element, such as silicon or germanium, or a compound, such as CdS or CdSe. These tiny particles can differ in color depending on their size. These glow a particular color after being illuminated by light. Due to the electronic properties, these nanomaterials are intermediate between those of bulk semiconductors and of discrete molecules. These Electronic characteristics of a quantum dot are closely related to its size and shape. The applications of Quantum Dots extends from Semiconducting materials, Optical materials, Quantum computing to Medical applications. The applications of Quantum dots are broadly studied in transistors, solar cells, LEDs, and diode lasers. Researchers have also investigated quantum dots as agents for medical imaging and as possible qubits in quantum computing. Quantum dot technology is one of the most promising candidates for use in solid-state quantum computation. Quantum dots are particularly significant for optical applications due to their high extinction coefficient. An immediate optical feature of colloidal quantum dots is their color. In modern biological analysis, Quantum dots proved to superior to traditional organic dyes in many ways, one of the most immediately obvious being brightness (because of the high extinction co-efficient combined with a comparable quantum yield to fluorescent dyes) as well as their stability (allowing much less photobleaching).