The concept and methodology of microarrays was in use as early as the 1980s. It was first introduced and illustrated in antibody microarrays (also as antibody matrix). Microarrays become notable when DNA microarrays emerged as an exciting new biomolecular tool capable of probing the entire transcriptome of the cell in the mid of 1990s. Nowadays, microarrays become widespread across genomic research and have a diverse range of applications in biology and medicine.