Cuneiform is one of the earliest known fully developed writing systems. Each character in cuneiform (from the Latin cuneous, wedge, and forma, shape) is formed by a combination of wedge- and nail-shaped strokes. Invented probably by the inhabitants of Sumer before 3000 BC, it was soon adopted by the Akkadians and then by other peoples, such as the Hittites and the Persians. The characters are stylizations of earlier pictographs, and were impressed in clay. Cuneiform was first deciphered in detail by Rawlinson in 1846.