The XPP-1 Plate Positioner is an accessory designed for use with IVIS optical preclinical imaging systems, for imaging experiments involving microtiter plates. It ensures repeatable placement of well plates within the imaging chamber, which is critical for bioluminescent and fluorescent signal detection. This alignment improves data quality, throughput, and reproducibility across experiments. The XPP-1 is autoclave-safe for sterilization and is intended for research use only, making it a valuable tool for high-throughput in vivo imaging workflows.