With OpenStack clouds growing to thousands of hypervisors and becoming geographically distributed, the Nova cells functions are being used to take on some of the challenges of running the largest OpenStack implamentations. Some of the major users of cells functionality will present their use cases which led to them to install more than one cell, covering planning, scheduling, configuration, limitations and upgrades. We will also cover the areas of ongoing work and enhancements to make it easier to use multiple cells.