DNA microarray technology,allowing massive hybridization of thousands of genes on a small area of a handful device,provides the ability of generating high throughput DNA hybridization data.Researchers are trying to compare the data that are generated from different biological sample to obtain the information of differential gene expression and clustering the data in order to find the co-expressed or co-regulated genes.However the basic principles of chemistry and chemical thermodynamics tell that the data comparison is not equivalent to the gene expression level comparison therefore in many cases will output distorted information,which lacks the fidelity and is untrue to the origin.The transcriptional gene expression profiling studies discuss on the basis of gene expression levels.Acquiring the expression levels of each gene is necessary for any further study.