The huge amount of genetic information available after completion of the DNA sequence requires the development of faster and cheaper analytical tools. This can be possible by miniaturising the analytical system itself and by the development of proper analytical procedures, involving fluidic processes. These procedures have three key requirements (specificity, sensitivity and time) that have to be improved. A precise genetic identifying technique is the ‘Fluorescence in situ hybridization’, that requires a controlled electrodes array on the bottom of a reservoir. Two types of devices are presented: a microarray of oligonucleotides probes obtained on a glass plate and a micromachined microarray of metallic electrodes obtained on a silicon wafer.