She said the vessels were flexible and in some cases their contents could be squeezed out.
"The microstructures that look like cells are preserved in every way," added Schweitzer, whose findings were published in the journal Science.
"Preservation of this extent, where you still have this flexibility and transparency, has never been seen in a dinosaur before." Feathers, hair and fossilized egg contents yes, but not truly soft tissue.
Studying the soft tissues may help answer many questions about dinosaurs. Were they cold-blooded like reptiles, warm-blooded like mammals, or somewhere in-between? How are they related to living animals?
Of course, the big question is whether it will be possible to see dinosaur DNA. "We don't know yet. We are doing a lot in the lab now that looks promising," Schweitzer said.
"Dinosaurs are relatively rare and we certainly think of Tyrannosaurus rex as being really rare -- although it really isn't -- so people tend not to want to cut holes into the bone or cut them in half," he said.