The whole point of a subnet is to establish a range of IP addresses that all exist on the same network. However, network divisions don't have to stop there. In fact, organizations may opt to further divide subnets into smaller groups for a variety of reasons, such as isolating particularly sensitive systems from the larger network, or just compartmentalizing different departments onto different networks. Whatever the reason, when deciding on a subnet, it is important to take into account how many further subnets can be created.