A common theme within this section (Si, Ge and Sn), is the use of bulky groups to stabilize species which are otherwise unknown. This includes the divalent species R2M, the trivalent radicals R3M0, and the multiply-bonded compounds R2M=MR2, R2M=CR2, etc. A significant difference from COMC is the much greater availability of single crystal x-ray diffraction and this is covered. Other important developments covered include, silicone polymers derived from carbofunctional silanes and the developments in polysilane high polymers. The Sn chapter covers the biggest development, the use of organotin compounds in organic synthesis, and this chapter provides the background information.