To investigate this, the pancreas was exposed in 8-week-old anesthetized NOD mice through a small abdominal incision, before being subjected to two-photon microscopy (Figure ). Baseline images were acquired following retro-orbital injection of Hoechst33342 and albumin-AF647 to label the nuclei and vasculature, respectively. Prior to LUXendin551 injection there was no detectable signal (Figure ). Rapid labeling occurred following the administration of LUXendin551 and was detected for at least 30 min post-injection (Figure ). These studies also demonstrated LUXendin551 is highly specific to islets and provides the ability to distinguish islets and beta cells from exocrine tissue (Figure ).