1. An array of immobilized molecules on a substratum that can be used to identify interacting molecules in a test solution. An increasing range of interactions can be tested, not just between nucleic acids (see gene chip), but also between proteins or between proteins and nucleic acids. The readout is often optical, with fluorescent reagents being added and microscopy allowing large numbers of samples (thousands) to be arrayed on each chip.
2. A silicon chip implanted into and functioning as part of a human body.