Fibroblasts are cells that are part of the connective tissue in the human body. The connective tissue has the role of supporting and connecting other tissues, but also is involved in regeneration, healing and immune responses. Skin, joints and bones are examples of structures where there is a large amount of connective tissue and fibroblasts.
Fibroblasts are "young" connective tissue cells that are able to produce collagen and other proteins that form the matrix of supportive structures. When a fibroblast has performed its role of producing connective tissue components, it becomes less active and transforms into a fibrocyte, which is a cell that lost the ability to produce collagen and other proteins. Fibroblasts are actively involved in healing of tissue damages and formation of scars.