Cardiac fibroblasts form one of the largest cell populations, in terms of cell numbers, in the
heart. They contribute to structural, biochemical, mechanical and electrical properties of the
myocardium. Nonetheless, they are often disregarded by in vivo and in vitro studies into
cardiac function. This review summarizes our understanding of fibroblast origin and identity,
their structural organization and role in myocardial architecture, as well as functional aspects
related to cell signalling and electro-mechanical function in the heart.