A small silicon chip developed at Stanford University School of Medicine uses photolithographic and genetic engineering techniques to study several thousand genes simultaneously. The thumbnail-size GeneChip, developed with Affymetrix of Santa Clara, Calif., carries an array of up to 100,000 DNA fragments, with which scientists can detect DNA-tagged genes like a bar-code scan. Using the technology, scientists could diagnose diseases and conduct biological and drug research faster and more efficiently.