Construction of a root observation laboratory, Soil Biotron, has recently been completed at the University of Michigan Biological Station in northern lower Michigan. The facility is located in a mixed northern hardwood forest about 70 years old, dominated by Populus grandidentata Michx., Acer rubrum L. and Quercus rubra L. The laboratory houses thirty-four window bays each containing sixteen removable glass pans permitting observation and direct access to roots and soil biota from the ground surface to 1.2 m depth. Equipment available for documenting activity of roots and soil invertebrates includes a trolley-mounted stereo-microscope, 35 mm still camera with macrolens, and a time-lapse video recording system. Ancillary data collected include: precipitation, wind speed and direction, relative humidity, wet and dry fall, soil temperature (four depths) and soil water content. In addition, the forest abutting the Biotron has been permanently gridded and the species of trees and their diameters recorded for allometric reconstruction of the forest.