It is one of the largest single works to have survived from the Roman Empire to the modern day and purports to cover all ancient knowledge. The work's subject area is thus not limited to what is today understood by natural history; Pliny himself defines his scope as "the natural world, or life".
The work is divided into 37 books, organized into ten volumes. These cover topics including astronomy, mathematics, geography, ethnography, anthropology, human physiology, zoology, botany, agriculture, horticulture, pharmacology, mining, mineralogy, sculpture, painting, and precious stones.
The Natural History became a model for later encyclopedias and scholarly works as a result of its breadth of subject matter, it’s referencing of original authors, and its index. The work is dedicated to the emperor Titus, son of Pliny's close friend, the emperor Vespasian, in the first year of Titus's reign. It is the only work by Pliny to have survived and the last that he published. He began it in 77, and had not made a final revision at the time of his death during the AD 79 eruption of Vesuvius.