piRNAs are the largest class of small non-coding RNAs related to but distinct from microRNAs, with known functions to silence transposons to maintain genomic stability and possible other functions beyond germline cells. Arraystar piRNA Arrays for human, mouse and rat use long oligonucleotide probes and duplex design to profile tens of thousands of piRNAs at high specificity and sensitivity, for the study its biology, molecular functions, and biomarker applications in germline, cancer and other cell types.