The document discusses the concept of 4D, which refers to three dimensions of space plus time as the fourth dimension. 4D is being implemented in various fields like filmmaking, aerospace, medicine, and computing. Some examples provided include 4D cinema which incorporates effects like movement and smells into the movie watching experience, 4D ultrasound which gives the impression of moving images in medical imaging, and 4D aircraft navigation which allows for on-time scheduling and closer aircraft spacing. The document also discusses a 4D virtual human caveman model created at the University of Calgary and 4D modeling software called CINEMA 4D.