The Get-WmiObject command is used to get classes:
Get-WmiObject Win32_Process -List
The WMI cmdlets are able to recursively list classes in namespaces. The following command lists classes in rootcimv2 and any child namespaces:
Get-WmiObject -List -Recurse
In addition to the list parameter, the WmiClass type accelerator might be used:
[WmiClass]"Win32_Process"