Firestore create a collection

[Pinelo92]

Pretty new to Firebase and i am not sure that if what i am asking is it possible. With that said, i am trying to implement a structure like this one ---> users(collection) ----> email(document) ----> New collection(collection) ...... I have gone through most of the code in scripts but i cannot figured out a way to add a collection nested to document. I can create a dictionary to document but my goal is to have a new collection attached to the doc. To make it more clear, projectName>users(col)>email(doc)>newCollection. Any idea?