In this talk we will introduce the shattered pellet injection (SPI) system currently being operated on ASDEX Upgrade. We will discuss the results of the laboratory characterization, during which over 1300 different pellets were fired and their post-shatter shard distributions analysed. Our results show that there is a significant discrepancy (for the largest and smallest fragments) between measured distributions and those predicted by the currently employed pellet break-up models. We will also discuss first results of the ongoing ASDEX Upgrade SPI campaign.