Microarrays and laboratories on a chip promise to revolutionise clinical practice and drug development. Experiments on tiny devices called microarrays could lead to new drugs, smarter diagnosis, and patient-centred prescribing by helping discover the genes that are involved in disease. Also known as a DNA chip or a gene chip, a microarray is a glass slide, nylon membrane or silicon chip, with thousands of different, application-specific DNA sequences, known as probes, fixed at different addresses on the chip's surface.