The cilium was one of the first organelles observed through a microscope.Motile cilia appear as oscil-lating cell appendages and have long been recognized to function in cell motility.In contrast,the far more widespread non-motile cilia,termed primary cilia,were thought to be vestigial and largely ig-nored following their initial description over a century ago.Only in the last two decades has the critical function of primary cilia been elucidated.Primary cilia play essential roles in signal transduction,chemical sensation,mechanosensation and light detection.Various microscopy approaches have been important for characterizing the structure,dynamics and function of the cilia.In this review,we dis-cuss the application of live-cell imaging technologies and their contribution to our current understand-ing of ciliary processes.