This paper introduces sigmoid or s-curve as a metaphor for describing the dynamics of change. We first encountered the s-curve as a description of a possible growth trajectory whereby populations become established, begin to flourish and the numbers increase rapidly until they reach some limit. At this point, the growth rate slows rapidly then stops and the size of the population is either maintained, something happens to stimulate a further upsurge in growth, or there is a dramatic decline. This basic biological metaphor has been picked up by social science researchers, particularly those who are interested in the complex dynamics of change and adaptation over time. The s-curve metaphor is now applied beyond population growth to describe change dynamics in social systems. We have noted this situation of rapid change followed by stability, further growth or subsequent decline in a number of projects we have worked on. The contributors to this special section discuss examples of this change pattern across a range of contexts.