Spatial organization in ciliary arrays In vivo the spatial organization of multiciliated cells and tissues is subject to several constraints. For instance, multiciliated tissues need to accomodate a variety of cell types, leading to areas devoid of cilia activity along a tissue. Furthermore, cilia must orient relative to each other within each cell and across the plane of the epithelium.Using a combination of live microscopy, molecular perturbations and quantitative image analysis we study how changes to the spatial organization of a ciliary array impacts the topology of the flows generated by it. We explore this question using the airway epithelium and multiciliated unicellular protists as models. hin layer of mucus. We are puzzled by the mechanisms that allow for proper function of ciliary arrays in these diverse physical contexts. To gain insight into this conundrum we study the planarian S. mediterranea.Planarians glide by secreting mucus on their ventral surface and use motile cilia to move the mucus. Their ventral epithelium is exposed, making this system amenable to perturbations in the surrounding fluid in vivo. By understanding how changes in the fluid impact flow properties and organism motility we aim to uncover the role of the physical environment in the function or a ciliary array.