Why do HPC in a cloud? How to do HPC (aaS), with GPU passthrough, in OpenStack? How to create full GPU HPC cluster, from scratch, on demand, under five minutes, all equipped with NVIDIA's DCGM and CUDA environment, and deep learning libraries/frameworks? Hybrid clouds with GPUs spanning OpenStack and AWS? How to easily and automatically move HPC user data and workloads between the private and public cloud? How to dynamically scale a virtualized HPC cluster, both horizontally (within private cloud) and vertically (to public cloud)? We'll answer these questions during a deep dive into the world of HPC on top of OpenStack and AWS. We'll discuss many ways OpenStack private clouds can be used for bursting HPC workloads, HPC-as-a-service, XaaS (anything-as-a-service), and creating hybrid clouds composed of on-prem private/community cloud OpenStack deployment, which dynamically scale them to public clouds, like AWS. Session includes demo.