The paper explores the process of development, establishment and recognition of "educational technology" as an independent scientific field and a separate teaching subject at universities. The paper points to: (a) the problems that this field deals with or should deal with, (b) knowledge needed for the profession of "educational technologist", (c) various scientific institutions across the world involved in educational technology, (d) scientific journals treating issues of modern educational technology, (e) the authors i.e. psychologists and educators who developed and formulated the basic principles of this scientific field, (f) educational features and potentials of educational technologies. Emphasis is placed on the role and importance of AV technology in developing, establishing and recognition of educational technology, and it is also pointed out that AV technology i.e. AV teaching aids and a movement for visualization of teaching were its forerunners and crucial factors for its establishing and developing into an independent area of teaching i.e. school subject. In summary it is stressed that educational technology provides for the execution of instruction through emission transmission, selection, coding, decoding, reception, memorization transformation of all types of pieces of information in teaching.