firebase simple - data structure questions

I have been reading a little about how to structure your firebase database and i understand that you need to split your data into pieces so you don't forced the client to download all of the 'users' data.

So in this example you will get all the users data when you write

  ref.('users').once('value', function(snap)...

    /users/uid
    /users/uid/email
    /users/uid/messages
    /users/uid/widgets 

but what if you specifically write the path to the location instead like

ref.('users/uid/email').once('value', function(snap)...

Will you still get all the users data or only the data in email ?