Cross-section micrographs of yellow poplar wood chips. (Top panel) Bright field microscopy shows composting effects on the cell wall structure over 24 weeks. (Bottom panel) fluorescence microcopy of the same field labeled by the Ct CBM3-GFP probe that binds to cellulose specifically. Increasing fluorescence intensity indicates higher cellulose accessibility to the probe. Ct CBM3-GFP: family 3a carbohydrate-binding module tagged by green-fluorescent-protein. wk: week.