Can I write a class using PowerShell?

With PowerShell being built on top of the .NET framework, can I write my own custom class using PowerShell?

I'm not talking about instantiating .NET classes... that part is plain enough. I want to write my own custom classes using PowerShell scripts. Is it possible? So far my research leads me to say that this isn't possible.

_{I'm still learning PowerShell, and so far I haven't found an answer on this website, despite a few searches.}