FIGURE 3. Tissue preservation in fossils.
From the following article:
Evolution of anatomy and gene control
Georgy Koentges
Nature 451, 658-663(7 February 2008)
doi:10.1038/451658a
a, Exquisitely preserved histology of muscle fibres with Z-banding and b, motor-axon endplates (arrows) in a 380-million-year-old placoderm. Scale bar: 20 
m. (From ref. 10, courtesy of the Royal Society.)