After extracting DNA from our sample, we then amplify it to make millions of copies of every sequence present.

The DNA (green) is then transcribed into an RNA copy (purple). And during the conversion, fluorescent molecules (red ball) are incorporated into the RNA copy. Later, when we see this fluorescence on a GeneChip® microarray, we will know that RNA in our sample has matched and bound to the DNA probe we built on the array.