Fibroblasts are mesenchymal cells which came from the embryonic mesoderm. They are important tools for a wide range of cellular and molecular studies, as they are one of the easiest types of cells to grow in culture. Their durability makes them amenable to a variety of manipulations ranging from gene transfection to microinjection. Fibroblasts secrete a non-rigid extracellular matrix that is rich in type I and/or type III collagen. They are responsible for synthesis of extracellular matrix in connective tissue and play a central role in wound healing. In the lymphoid compartment, human lymphatic fibroblasts construct a unique conduit system with intriguing size exclusion; which plays a fundamental role in regulating immune response and homeostasis of tissue fluids.