A quantum dot is a nanoscale semiconductor structure, typically composed of materials like cadmium selenide or indium arsenide, that exhibits unique quantum mechanical properties. These properties arise from the confinement of electrons within the dot, leading to discrete energy levels, or "quantization" of energy, similar to the behavior of individual atoms or molecules. Quantum dots have a size on the order of a few nanometers and can emit or absorb photons (light) with precise wavelengths, determined by their size, making them valuable for applications in fields such as optoelectronics, quantum computing, and as fluorescent markers in biological imaging. Their ability to tune the color of emitted light by varying their size has led to their widespread use in displays, lighting, and various other technologies.