TTT-plotting -- a tool for both theoretical and practical problems. During the last ten years the scaled total time on test (TTT-)transform and its empirical counterpart, the TTT-plot, have proven to be very useful in different applications in reliability (e.g. model identifications, replacement theory and burn-in problems). Some of these applications is touched in this expository paper. Furthermore, it is indicated how the TTT-concept can be used as a source of inspiration in some research situations.