Sensor network development is notoriously difficult due to the low visibility of sensor platforms and systems. We propose sensornet checkpointing to increase the visibility of sensor networks. With sensornet checkpointing, we transfer network-wide application checkpoints between simulated and real networks. This approach enable advances in many research areas: visualization, repeatable experiments, fault injection, and application debugging. We demonstrate sensornet checkpointing on a network of Tmote Sky motes running Contiki.