In the morphological stages of tooth development the Bud Stage is followed by Cap Stage. In Bud Stage as the Enamel Organ grows in size it develops a concavity and attains a cap shape which then increases in size. This change in shape is because of unequal growth in different parts of the Enamel Organ. The tooth germ appears like a cap of Enamel Organ kept over a ball of condensed ectomesenhcyme. A basement membrane surrounds the Enamel Organ. Thus the Cap stage shows morpho-differentiation by changing its shape from a bud to a cap, and also there is histodifferentiation from this stage. That is, the cells of the Enamel organ start showing differentiation or specialization. From the 2 types of cells in Bud stage, 3 types of cells are seen in the Cap stage. A single layer of cells lining the convex surface of the cap form the Outer Enamel Epithelium which are cuboidal in shape. A single layer of cells lining the concave surface form the Inner Enamel Epithelium which are tall columnar in shape. These cells later differentiate into Ameloblasts and form enamel. And the cells in the center between the Inner and Outer Enamel Epithelium are called the Stellate Reticulum which are star shaped. It is sometimes also referred as Enamel Pulp. The central cells in Bud stage are polygonal shaped, then in Cap stage they change to star shape. This is because the cells in the center start releasing glycosaminoglycans in to the surrounding ground substance. The glycosaminoglycans are hydrophilic and so attract water from the surrounding connective tissue. This collection of water pushes the cells apart but they remain attached to each other at points of intercellular junctions. This gives an appearance of a network of star shaped cells, hence called Stellate Reticulum. The collection of water gives Stellate Reticulum a cushion like consistency. Thus, the function of Stellate Reticulum is to protect the important Inner Enamel Epithelium from any mechanical trauma by acting as a shock absorber. The junction of Inner Enamel Epithelium and Outer Enamel Epithelium is known as the Cervical Loop. It is an area of intense mitotic activity, as the size of the cap rapidly increases in this direction. The Dental Lamina still attaches the Enamel Organ to oral ectoderm. Sometimes, in a histological section two or more dental lamina may be seen with entrapped ectomesenchyme. This entrapped ectomesenchyme is called as Enamel Niche. This appearance is not because there are 2 Dental Lamina, it is because of the fact that the Dental Lamina is a 3 dimensional plate which is seen in 2 dimensional section. So if the Dental Lamina is curved in some place, in a 2 dimensional view of the cut section it appears as if 2 lamina are present. There are few structures known as 'Transient structures' or 'Temporary structures' of enamel organ. These structures form in the cap stage and then disappear before enamel formation begins. Enamel knot is a structure of dense collection of cells in Stellate Reticulum just above the Inner Enamel Epithelium. If the densely packed cells form a vertical extension towards the Outer Enamel Epithelium it is called Enamel Cord. If the vertical extension of densely packed cells reaches the Outer Enamel Epithelium it is Enamel Septum. As it now divides the Stellate Reticulum into two compartments. The area on the Outer Enamel Epithelium where the Enamel Septum meets, shows slight concavity called Enamel Navel as it looks similar to the umbilicus or navel on the abdomen. Enamel knot, cord and septum, act as a reservoir of dividing cells in a rapidly growing enamel organ. Additionally Enamel Knot acts as a signaling center and plays an important part in deciding what shape of the tooth is to be formed. All these structures are temporary and disappear before enamel formation begins. That was about the epithelial part of the tooth germ, coming to the surrounding connective tissue. The dense collection of ectomesenchymal cells below and around the enamel organ called 'ectomesenchymal condensation' continues to show proliferation. This area can now be roughly differentiated into 2 parts, the cells which are within the concavity of the Enamel Organ and below it form Dental Papilla, which later form pulp and dentin. The ectomesenchyme surrounding the Dental Papilla and Enamel Organ is called the Dental Sac or Dental Follicle, which later forms cementum, periodontal ligament and alveolar bone.