DNA Chips - DNA chips are thin wafers of silicon glass carrying many different oligonucleotides synthesized at a very high density (300,000 to over 1 million oligonucleotides/cm2) directly onto the wafer. The oligonucleotides are synthesized at a high spatial resolution and in precise locations; each oligonucleotide has the sequence of a different gene present in the genome.

Therefore, sequence information for the genes to be represented in the DNA chip must be available.

The oligonucleotide synthesis is based on two techniques called photolithography and solid phase DNA synthesis; it uses a series of building blocks that contain photochemically removable protective groups.