Trying to understand pod resource versions and why they change

I’m developing a controller and trying to learn the inner-workings of K8s.

I noticed that a pod’s resource version can change even though it appears nothing else in pod.Spec, pod.Status and pod.ObjectMeta changes.

Does anyone know why this is? I’ve observed this on a version 1.11.5 cluster and a 1.13.3. cluster.

I’m also unable to do anything that triggers a pod update. What kinds of things would trigger a pod update?

Thanks for any insight.