Fibroblasts, are mesenchymal cells from the embryonic mesoderm. Fibroblasts secrete a non-rigid extracellular matrix that is both rich in type I and/or type III collagen. They are responsible of the synthesis of extracellular matrix in connective tissues and play a central role in wound healing. They are useful tools for a wide range of cellular and molecular studies, as they are one of the easiest types of cells to grow in culture. In addition, their durability makes them amenable to a variety of manipulations ranging from gene transfection to microinjection. Immortalized Human Small Intestine Fibroblasts are an excellent tools to study the small intestine physiology and also the mechanisms of carcinogenesis. Immortalized Human Small Intestine Fibroblasts are useful tools to understand the highly integrated balance between proliferation, differentiation, and cell death. This cell line also allow to stablish in vitro models for HIgh Throughput and High Content Screening.