This project will provide significant new information about how single cells are able to squeeze through tight spaces, by understanding how the scaffolds that support cell shape are remodeled and coordinated. Cells come in all shapes and sizes and often need to move through constricted spaces to perform their functions. The mechanisms that allow small cells to move quickly and nimbly can be conserved between different organisms, from the smallest nematode worms to humans. Specifically, this project will focus on proteins named septins, which can act like a girder to protect cells as they crawl through constrained environments. The primary aim of this project is to understand how evolutionarily conserved septin proteins function similarly or differently under varied conditions, including in the human immune system and in migrating worm cells. Septin protein function will be studied, in part, by developing specialized microscopy techniques that to allow observing cells moving within dense tissues and tight environments. This project will also train undergraduate and graduate students, and is designed to provide specialized training in biology, optics, and computational analysis approaches. In order to share discoveries and inspire the broader community, modules on cell movement and microscopy will be made available to local high schools and incorporated into outreach activities. Cell migration is critical for organismal development and cellular function. Despite the