Admission control takes place before Kubernetes processes the request and after authentication and authorization are passed. It's enabled when launching API server by adding --admission-control parameter. Kubernetes recommends officially to have the following plugins with the cluster if the cluster version is >= 1.6.0.
--admission-control=NamespaceLifecycle,LimitRanger,ServiceAccount,PersistentVolumeLabel,DefaultStorageClass,DefaultTolerationSeconds,ResourceQuota
The following introduces the usage of these plugins, and why should we need them. For more latest information about supported admission control plugins, please visit official document https://kubernetes.io/docs/admin/admission-controllers.