The majority of surviving examples of Maya writing are from the Classic period (AD 250-900) although earlier inscriptions date to the Late Preclassic (400 BC - AD 250). The origin of the script is complex and far from clear.
Maya writing has been found on monumental sculpture, public buildings, murals, pottery, portable objects (made of shell, obsidian, bone, wood, jade and other stones) and screenfold books, called codices. The inscriptions deal mainly with calendrical and astronomical information, and historical events such as alliances, wars, lineages and marriages.
The text was inscribed in blocks placed in horizontal and vertical rows. One or more glyphs were set in each of these blocks. The reading order within each block is generally from left to right and top to bottom. Two columns were read together following the same order. The text appears sometimes in single columns, in L-shape or other arrangements (see, for example, the Yaxchilán Lintels).
Maya hieroglyphs were first identified as a writing system during the nineteenth century, when the bar-and-dot numerical system was deciphered. In the 1950s it was discovered that the script combined signs representing whole words with signs representing syllables. Certain glyphs were recognized as naming specific people and cities (known as Name Glyphs and Emblem Glyphs respectively). There were major breakthroughs in decipherment in the second half of the twentieth century and approximately 85% of the glyphs can now be read.