We pick g.root-servers.net, one of the 13 root servers (1), and ask it about maniac.fim.uni-passau.de and learn that de is delegated to five name servers (2), so we ask f.nic.de where we learn that uni-passau.de is delegated to four name servers, including ns.fmi.uni-passau.de (3), so we ask that one and get the following answer: