A quantum dot is a particle of matter so small that the addition or removal of an electron changes its properties in some useful way. All atom s are, of course, quantum dots, but multi-molecular combinations can have this characteristic. In biochemistry, quantum dots are called redox groups. In nanotechnology, they are called quantum bits or qubit s. Quantum dots typically have dimensions measured in nanometers, where one nanometer is 10 ^-9 meter or a millionth of a millimeter. The fields of biology, chemistry, computer science, and electronics are all of interest to researchers in nanotechnology. An example of the overlapping of these disciplines is a hypothetical biochip, which might contain a sophisticated computer and be grown in a manner similar to the way a tree evolves from a seed. In this scenario, the terms redox group and qubit are equally applicable; it is hard to classify such a chip as either animate or inanimate. The quantum dots in a biochip would each account for at least one data bit, and possibly several. In the extreme, the position of a single electron in a quantum dot might attain several states, so that a quantum dot could represent a byte of data. Alternatively, a quantum dot might be used in more than one computational instruction at a time. Other applications of quantum dots include nanomachines, neural networks, and high-density memory or storage media