Second-harmonic generation (SHG) images of collagen and the relationship between collagen and elastin fibers. (A-F) SHG images of collagen which show its zonal structure were taken from fresh articular cartilage samples from kangaroo femoral condyle from both transverse and longitudinal views. These images resemble Figure 3 of our article . (a-f) Collagen and elastin fibers in the superficial zone of articular cartilage from both transverse and longitudinal views and their relationships. Collagen was imaged by collecting SHG signals, and elastin fires were imaged by collecting sulforhodamine B fluorescent signals. Images (a-f) resemble Figures 5 and 6 of our article . X and Y coordinates indicate images that were parallel to the cartilage surface and taken from a transverse view; X and Z coordinates indicate images that were vertical to cartilage surface and taken from a longitudinal view.