X-ray transmission images of a kidney tissue fixed with glutaraldehyde (G). All the X-ray absorption images are shown in colour and black and white to better highlight transmission values and morphology, respectively. First and third rows show the same absorption images (in different scale colour) at Rad1 radiation dose. Second and fourth rows show the same areas at further radiation doses (Rad2, Rad3 and Rad4 as specifically indicated). The scale bars represent 20 µm.