As education is a global concern, utilising educational technology to facilitate teaching and learning activities has been widely practised almost everywhere at every minute for decades. Revisiting the historical development of a particular technology is noteworthy to education practitioners, historians and various interested parties. Concerning the evolution of educational technology, most of the existing literature has focused on a rather brief period and often comes with fragmented, incomprehensive or oversimplified descriptions. In addition, some of the major literature was written several decades ago and further updates are desirable. In view of these considerations, this paper aims to contribute a comprehensive and updated examination of the transformation of technologies into educational technology from the late nineteenth to the early twenty-first century. In particular, this paper scrutinises five technologies in their contexts of historiographical transformation: audio technology, such as phonography and radio; visual technology, such as silent films; audio and visual technology, which includes sound film and television; computing technology, which covers personal computers and the Internet; and asynchronous learning technology, which embraces course management systems and video conferencing packages, and synchronous learning technology. Briefly, this paper looks into when, why and how the technologies were transformed into educational technology with pedagogical implications. This paper is useful for education practitioners by stimulating them to devise more educational technology to cater for various educational needs. Besides, by illustrating how technology shapes education, this paper also helps historians and other practitioners by enriching their understanding of the connection between technology and different aspects of people's livelihoods.