Mary Schweitzer sits at a microscope in a dim lab, her face lit only by a glowing computer screen. After 68 million years in the ground, a Tyrannosaurus rex found in Montana was dug up, its leg bone was broken in pieces, and fragments were dissolved in acid in Schweitzer's laboratory at North Carolina State University. Last year ... Schweitzer announced she had discovered blood vessels and structures that looked like whole cells inside that T. rex bone - the first observation of its kind. The finding amazed colleagues, who had never imagined that even a trace of still-soft dinosaur tissue could survive. The observations could shed new light on how dinosaurs evolved and how their muscles and blood vessels worked. And the new findings might help settle a long-running debate about whether dinosaurs were warmblooded, coldblooded - or both. In the lab, Wittmeyer now takes out a dish with six compartments, each holding a little brown dab of tissue in clear liquid, and puts it under the microscope lens. Inside each specimen is a fine network of almost-clear branching vessels-the tissue of a female Tyrannosaurus rex that strode through the forests 68 million years ago, preparing to lay eggs. Of course, what everyone wants to know is whether DNA might be lurking in that tissue. Wittmeyer, from much experience with the press since the discovery, calls this the awful question" - whether Schweitzer's work is paving the road to a real-life version of science fiction's Jurassic Park, where dinosaurs were regenerated from DNA preserved in amber.