Experiment PP216 is an experiment in a larger project the Vault 101's vault physician James performed in 2274.
Background[]
"PP" stands for Project Purity while "216" stands for Revelation 21:6. James, according to his notes, "borrowed" some water chips and rerouted the Clinic's power supply in order to perform unsanctioned personal experiments. The results in the notes are vague but optimistic. He also notes that this is the first time that his assistant Jonas Palmer had helped in him in this project.
The Lone Wanderer can read the notes for this experiment from the Vault 101 medical data system in their Dad's terminal located in the physician's office on August 3, 2274.
Behind the scenes[]
James "borrowing" water chips is a reference to Vault 13, which had a broken water chip, kickstarting the events of Fallout.