This report provides an overview of the development and applications of DNA-based microarrays and biochip technology in genomics. DNA microarrays and biochip technologies are having a significant impact on a wide variety of areas in genomic research. Many fields, including gene discovery, drug discovery, toxicological research, and medical diagnostics, will benefit from the use of DNA micro array and biochip technologies. High-density micro array chips with relatively large detection systems are useful in the research laboratory for monitoring the expression of large numbers of genes in parallel. On the other hand, small and inexpensive integrated biochips that combine probe arrays with sensor microchips are most suitable for medical diagnosis at the site-of-care.