There are millions of copies of goose DNA probes (ATCATG) in a single square on the array. And washing over those probes are millions of pieces of RNA from every organism present in the food sample. It's like the world's largest molecular singles bar. All of the strands from every genome are swimming around, looking for their perfect complement — molecular true love on a microarray. If RNA prepared from the food sample is from goose, it will match the goose DNA probe we designed.