text: With the discovery of the dual-membrane nature of mitochondria, the pioneers of mitochondrial ultrastructural research proposed different models for the organization of the mitochondrial inner membrane. Three models proposed were:
  *Baffle model – According to Palade (1953), the mitochondrial inner membrane is convoluted in a baffle-like manner with broad openings towards the intra-cristal space. This model entered most textbooks and was widely believed for a long time.
  *Septa model – Sjöstrand (1953) suggested that sheets of inner membrane are spanned like septa (plural of septum) through the matrix, separating it into several distinct compartments.
  *Crista junction model – Daems and Wisse (1966) proposed that cristae are connected to the inner boundary membrane via tubular structures characterized by rather small diameters, termed crista junctions (CJs). In the middle of 1990s these structures were rediscovered by EM tomography, leading to the establishment of this currently widely accepted model.
  More recent research (2019) finds rows of ATP synthase dimers (formerly known as "elementary particles" or "oxysomes") forming at the cristae. These membrane-curving dimers have a bent shape, and may be the first step to cristae formation. They are situated at the base of the crista. A mitochondrial contact site cristae organizing system (MICOS) protein complex occupies the crista junction. Proteins like OPA1 are involved in cristae remodeling.
  Crista are traditionally sorted by shapes into lamellar, tubular, and vesicular cristae. They appear in different cell types. It is debated whether these shapes arise by different pathways.