This detailed book explores the fundamentals of myofibroblast biology in tissue repair, fibrosis, and tumors as well as providing cutting-edge laboratory methods used to investigate myofibroblast functions in physiological and pathological settings in vitro and in vivo, as written by leading academic scientists. Section I of this volume focuses on fundamental methods to study myofibroblast biology and covers topics such as methods for detecting myofibroblasts and senescent myofibroblasts in cell culture and histology, single cell RNA sequencing to identify myofibroblast subsets in fibrotic tissues, and functional assays to assess TGF-β activation, myofibroblast apoptosis, or matrix deposition and crosslinking. Section II discusses methods to investigate the mechanobiology of myofibroblasts in vitro, including the fabrication of functional hydrogels with tunable stiffness, the use of atomic force microscopy to characterize matrix and cellular stiffness, as well as molecular assays to assess fibroblast mechanotransduction pathways and durotaxis. Section III describes multiple animal models to investigate myofibroblast functions across organs in vivo as well as human organoid systems, precision tissue slices and decellularized 3D tissue scaffolds to assess myofibroblast functions in relevant human ex vivo models. Written for the highly successful Methods in Molecular Biology series, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols, and tips on troubleshooting and avoiding known pitfalls.  Authoritative and extensive, Myofibroblasts: Methods and Protocols is an essential collection for researchers delving into the processes and effects of these important cells.