  The last decade has seen tremendous developments in memory and storage
technologies, starting with Flash Memory and continuing with the upcoming
Storage-Class Memories. Combined with an explosion of data processing, data
analytics, and machine learning, this led to a segmentation of the memory and
storage market. Consequently, the traditional storage hierarchy, as we know it
today, might be replaced by a multitude of storage hierarchies, with
potentially different depths, each tailored for specific workloads. In this
context, we explore in this "Kurz Erkl\"art" the state of memory technologies
and reflect on their future use with a focus on data management systems.
