This array includes 1,046 different DNA oligonucleotides, each specific for a particular cDNA sequence generated from the mRNA transcriptome of a particular tissue. The cDNAs are fluorescently labelled and applied to the chip.  Quantitative patterns of gene activity are indicated by pseudo-colours: high levels of binding (and thus high levels of mRNA expression) are indicated by "hot" or "warm" signals, while "cool" and "cold" signals indicate low expression.