The amplified (or unamplified) nucleic acids are directly labeled with a fluorescent dye (Cy3 or Cy5) using random priming with the Klenow fragment of DNA polymerase for DNA (Wu et al., 2006a) or Superscript TM II/III RNase H-reverse transcriptase for RNA (He et al., 2005b) . The labeled DNA/RNA is then purified and dried for hybridization.