SAMPLING PERMIT:
As in all National US Parks, removal of any object from the Park you have not brought in or bought in the Park is not allowed.  To take samples for scientific research requires obtaining a sampling permit in advance and is covered by the international Budapest Treaty..

GENERAL INFORMATION:
 The official information about Yellowstone National Park can be obtained easily from the extensive website http://www.nps.gov/yell/  with the subsite http://www.nps.gov/yell/planvisit/ and the interactive map from Yellowstone http://www.nps.gov/yell/planvisit/orientation