The newly designed probe sets can then be commercially synthesized. Several options are available for producing arrays. Synthesized oligonucleotide probes can be spotted onto nylon membranes or glass slides (Taroncher-Oldenburg et al., 2003; Rhee et al., 2004; Tiquia et al., 2004) . Glass slides are more frequently used since they have less background fluorescence (Schena et al., 1995 (Schena et al., , 1996 and allow higher probe density (Ehrenreich, 2006) . Probes can also be added to slides using bubble Jet printing (Okamoto et al., 2000) , laser-induced forward transfer (Serra et al., 2004) , or photolithography (Chen et al., 2009 ). In addition, a few companies, such as Agilent or Affymetrix, synthesize custom microarrays using a customer's probe set.