One way of fabricating DNA microarrays is to spot pre-synthesized oligonucleotides directly onto a glass plate. In this issue (p. 438 ), Okamoto et al. improve on this method using a miniaturized “Bubble Jet” device to spot the oligonucleotides. Their technology ejects picoliter sized droplets onto the glass surface, with lower cost and greater uniformity than existing microspotting technologies. They further enhanced the robustness of the microarrays by spotting onto a glass surface coated with bifunctional crosslinkers that covalently bind to a thiol group at one end of the oligonucleotides probes. They demonstrated that microarrays fashioned by this method could be used to distinguish single base mismatches from perfect matches after probing with synthetic oligonucleotides or PCR amplified fragments.