**2.1. Introduction**

Thyroid tissue fragments were kept on glass in saline solution, or *in vitro* (as this involved a glass vessel). Established the neuron cell theory, it has since been established that the unit of life is a cell (i.e. cell theory 1910) and cell culture or *in vitro* study began [35]. Cell cultures were then developed, thereby leading to studying cell functions in controlled conditions and different descriptions of culture mediums, supports and conditions have been developed from 1910. Fibroblasts in culture leave a matrix on culture surface on which endothelium cells from blood capillaries can be cultured; this has been called an extracellular matrix (ECM) [36]. Extracellular supports close to the ECM surrounding cells *in vivo* (such as collagen, laminin, fibronectin or matrigel) are currently being used [37].

New culture techniques were developed in 1975 in view of the close structure-function relationship, recognising the importance of organs' functional units, such as isolating and culturing isles of Langerhans from the pancreas [38] or "acini" regions from the lactant mammary gland or epithelial structures which needed to be conserved in polarised cell culture [39]. Thyroid follicle incubations and cultures could also be mentioned here.

A brief description of the most pertinent techniques for culturing the thyroid, isolated thyrocytes and/or thyroid follicles is given below.
