The primary cilium - once a "rudimentary" organelle that is now a ubiquitous sensory cellular structure involved in many pathological disorders.

This article looks mostly at the steps that have led to the primary cilium finding its place in our understanding of cell biology, developmental biology, and medical syndromes due to its aberrations. It is a personal account that stresses, if nothing else, the value of the adage "stick to your guns". My obsession with this organelle, following on from fascination with the centriole, has led to a whole career devoted to determining the nature and role of primary cilia in basic cell biology, which has proved much more important than had been appreciated for almost a century. They are heavily involved in very many aspects of cell physiology that have much wider implications with regard to human biology and probably throughout the animal kingdom. That aberrations, to the surprise of many researchers in their structure or functioning has led to their being implicated or perhaps deeply involved in an extraordinary range of medical conditions. This invitation allows me to raise crucial questions that need answers regarding the regulation of their genesis, their cache of both intracellular and extracellular signal, and their association with a multitude of development processes from embryo to adult status.