DNA microarray or chip is a new technique in molecular biology.With combining the light-directed chemical synthesis, semiconductor-based photolithography,and solid-phase chemical synthesis, thousands of oligonucleotide probes were arrayed or spotted on the surface of solid support. This technology has successfully monitored the simultaneous expression of many thousands of genes, developed to screen DNA mutation and polymorphism, applied to sequence DNA, and discovered the novel disease-related genes by hybridization to radioisotope or fluorescence labeled DNA or cDNA coming from interesting tissues and cells.