The Rhynie chert.

In 1912, William Mackie, a medical practitioner surveying the regional geology west of Aberdeen, Scotland, happened on some unusual rocks (Figure 1) near the village of Rhynie. Dark gray to nearly black and shot through with cylindrical structures a few millimeters in diameter, these rocks differed markedly from the shales and volcanic rocks of local hills. Mackie had discovered the Rhynie chert - paleobotany's most iconic deposit - with its exceptionally preserved fossils that provide a uniquely clear view of early terrestrial ecosystems in statu nascendi. Early research by Robert Kidston and William Lang showed that the cylindrical structures in Rhynie rocks were the axes of early plants, preserved in remarkable cellular detail. A century of subsequent research confirmed that Rhynie provides not only an unparalleled record of early tracheophyte (vascular plant) evolution, but also offers additional paleontological treasures, including animals (mostly arthropods) and microorganisms ranging from fungi, algae, and oomycetes to testate amoebozoans, and even cyanobacteria. A captivating snapshot of life on land more than 400 million years ago, the Rhynie chert provides our earliest and best view of how terrestrial ecosystems came to be.