The development and progression of cancer and the experimental reversal of tumorigenicity are companied by complex changes in the pattern of gene expression.DNA micro-array technology is used to profile complex disease and discover novel disease-related genes. This technique has been successfully used to investigate gene expression in processes as complex as inflammatory disease, tumor suppression and to identify heat shock in human T cell.DNA micro-arrays or DNA-chip technology allows expression monitoring of hundreds and thousands of genes simultaneously and provide a format for identifying genes as well as changes in their activity. The DNA micro-array helps us study genome-wide expression patterns in complex biological systems. These tools have shown great promise in finding the meaning of complex diseases such as cancer.There is some interest in the potential application of DNA micro-array analysis for gene expression profiling in human cancers. Micro-arrays of DNA provide a powerful tool for studying the development and progression of cancer phenomena. It might be useful for tumor classification, for the elucidation of regulatory networks that are disturbed in tumor cells and for the identification of genes that might be of use for diagnostic purposes or as therapeutic targets.