sub forums or different forums

Is it possible to create a sub forum within a another forum?

Somthing like this I guess:

• Biology
• Zoology
• Q&A
• Lounge
• Journals
• Botany
• Q&A
• Lounge
• Journals
• Evolution
• Q&A
• Lounge
• Journals
• Chemistry
• Physics

So what you would see on the first or header page of the forum is Biology, Chemistry and Physics with the first bunch of sub sections. Then when you click on the Sub section it opens up with the discussion areas proper.  I hope that makes sense. To get a better idea of what I mean, check the LOUNGE are of the www.htmlforums.com for the sub section called GAMES.

If this can't be done then I have another question. Is it possible to have multiple forums on one web server that can use a single log on username and pasword. So that a user can switch between these forums without haivng to log in and out.

I have had a search of these forums already and am still doing so.

Thanks in advance for any help.