The concept of complexity is a popular and contentious topic. Just what is complexity? What does it mean to 'think complexly'? This paper addresses both of these issues. Complexity thinking is impossible to define with any precision as it deals not only with change, dynamic change, evergoing, but with transformative change. Definitions require stability, the very element complexity neither has nor aspires to have. Instead complexity asks us to see, to deal with a world in continual flux; but a world that does have patterns to it, patterns that bind and structure through their interplay. In short, complexity seeing/thinking asks us to envision our world and events within that world in terms, not of 'things' but of process. In so doing, we are moving from a science that studies particles to the new sciences of chaos and complexity that study the interactive relations between and among particles, events, happenings. After distinguishing the similarities and contrasts between chaos and complexity, and showing the characteristics of each, along with looking at systems closed and open, frames modern and post-modern, this paper enumerates practical aspects of thinking complexly: accepting ambiguity, allowing humility to permeate one's being, and seeking out and utilizing difference and diversity. The health care profession by its very nature of dealing with that which is dynamically living deals with the complex daily. Its routines and rules, though, are too often caught in a modernist trap. This paper challenges all health care professionals to break free from that trap, and suggests ways to do so.