DNA microarrays are the modern, parallel version of classic molecular biology hybridization techniques allowing the exploration of thousands of sequences in a single run. The technique permits the complete analysis of genetic material and the monitoring of expression changes occurring in a biological sample under various conditions. Microarrays have been used successfully in various research areas including: sequencing, single nucleotide polymorphism (SNP) detection, characterization of protein-DNA interactions, DNA computing, mRNA profiling, and many more. Applications of microarrays in the biosciences include: gene expression studies, disease diagnosis, pharmacogenomics, drug screening, pathogen detection, and genotyping.This book focuses on the current successful applications of microarrays in various areas of bioscience. The authors describe the use of microarrays to assist basic research and drug discovery by the generation of gene expression maps, the reconstruction of gene networks and the study of biochemical pathways, the classification of genes and biological samples, and a real case study on the transcriptional effects of vaccine treatment. An entire chapter is dedicated to applications of microarrays that do not involve gene expression.