Even those whose contact with paleontology was limited to toy dinosaurs as children know that fossilization means the gradual replacement of organic material by minerals, and that over millions of years, all that's left is rock in the shape of bone. If scientists are lucky, conventional paleontological wisdom goes, they might get an imprint of skin or feather left in the mud and then hardened. Nobody would ever imagine that soft tissues would ever survive the fossilization process.
Time to rewrite the biology texts. Dr. Mary Schweitzer of North Carolina State University and Montana State University has managed to extract blood vessels and fibrous tissues (good pictures here) from the interior of a fossilized Tyrannosaurus rex femur found in 2003. The bone had to be broken in two in order to be lifted from its resting place, and researchers noticed that the interior of the fossil wasn't quite as solid as the exterior. Schweitzer used a mild acid to dissolve the mineral components, leaving organic material which was stretchy and pliant, with well-defined blood vessels and cell structures. Schweitzer went on to duplicate the process with three more dinosaur specimens, two more T. rex and a hadrosaur.
The research as it stands demonstrates a close structural resemblance at the microscopic level between the dinosaur tissues and large birds such as ostrich -- hardly a surprise to those of us who have continued to follow paleontology well past the toy dinosaur phase, but a welcome confirmation of current theory. Given the obvious Jurassic Park jokes, paleontologists are being very cautious about any notion that DNA could be extracted from the tissues, but do suggest that proteins could be identified. 65 million year old proteins would be a tremendous boon to our understanding of evolutionary biology.