This image shows an optical micro-picture of a small part of a 484 series SQUID array showing 54 SQUIDs and a high resolution picture showing only 11 SQUIDs. The array is fabricated by optical lithography after depositing a YBa2Cu3O7 thin film on a SrTiO3 bicrystal. Each SQUID consists of two Josephson junctions connected in parallel. The Josephson junctions (schematically represented as red crosses) can be seen as 3 micron-wide narrow bridges crossing the bicrystal boundary shown with a dotted line. Each pair of successive SQUIDs is connected in series via inductive large area narrow flux-focusers (one is highlighted with a red U-shape). The flux inside each SQUID hole is quantized. Flux coherency in the array is reached when each SQUID hole is penetrated by the same number of integers of flux quanta.