The history of educational technology can be traced back to early tools like cave paintings that were used to transmit knowledge. Throughout history, advances in technology stimulated new instructional techniques, from early writing systems to the printed book and modern digital technologies. Major developments include the introduction of audio-visual aids in the early 20th century, the emergence of computer-based learning in the 1950s and 1960s, the rise of online learning and digital communications in the late 20th century, and the growing use of mobile technologies today. Educational technology has evolved from early tools to increasingly sophisticated applications of technology to support teaching and learning.