Cai Lun in the context of "Eastern Han dynasty"

Paper is a thin sheet of matted cellulose fibers. Largely derived from lignocellulose, paper is created from a pulp dissolved into a slurry that is drained and dried into sheets. Different types of paper are defined by constituent fiber, paper pulp, sizing, coating, paper size, paper density and grammage.

The papermaking process developed in East Asia at least as early as 105 CE by the Han court eunuch Cai Lun, although archaeological evidence exists of 2nd century BCE paper-like material in China. Before the industrialization of paper production, the most common paper was rag paper, made from discarded natural fiber textiles collected by ragpickers. The 1843 invention of wood pulp, coupled with the Second Industrial Revolution, made pulpwood paper the dominant variety to this day.

Paper is a thin nonwoven material traditionally made from a combination of milled plant and textile fibres. The first paper-like plant-based writing sheet was papyrus in Egypt, but the first true papermaking process was documented in China during the Eastern Han period (25–220 AD), traditionally attributed to the court official Cai Lun. This plant-puree conglomerate produced by pulp mills and paper mills was used for writing, drawing, and money. During the 8th century, Chinese paper making spread to the Islamic world, replacing papyrus. By the 11th century, papermaking was brought to Europe, where it replaced animal-skin-based parchment and wood panels. By the 13th century, papermaking was refined with paper mills using waterwheels in Spain. Later improvements to the papermaking process came in 19th century Europe with the invention of wood-based papers.

Although there were precursors such as papyrus in the Mediterranean world and amate in the pre-Columbian Americas, these are not considered true paper. Nor is true parchment considered paper: used principally for writing, parchment is heavily prepared animal skin that predates paper and possibly papyrus. In the 20th century with the advent of plastic manufacture, some plastic "paper" was introduced, as well as paper-plastic laminates, paper-metal laminates, and papers infused or coated with different substances to produce special properties.