Can't expand To/CC/BCC field in Android

Edit: In the Android mobile app Beta, I can’t see an easy way to view all the recipients of an email. The best I can do is select “view header” from the message options, then scroll past all the code to find the fields I need. Alternately, I can “reply all” and see who is added to the To/CC fields. Neither is particularly convenient. Maybe I’m missing something obvious!