As part of the respiratory chain, c-type cytochromes are essential electron transporters. They are characterized by the covalent attachment of a heme prosthetic group. The biogenesis of these proteins includes all the processes leading to this fixation. Yeast and animals have evolved a comparatively simple mechanism relying on cytochrome c heme lyases. In contrast, plant mitochondria have kept a maturation pathway inherited from their prokaryote ancestor. It involves Ccm proteins encoded in both the nuclear and the mitochondrial genomes of plants. These proteins compose a heme delivery pathway, include an ABC transporter, a redox protein and a putative heme lyase.