Molecules are two or more atoms held together by chemical bonds. When an atom of a molecule is held or moved, the rest of the atoms in a molecule move, so long as they are bonded. Harvesters collect atoms from the enviormental background outside the reactor in production assignments. Storage tanks serve the same purpose of harvesters, albeit larger. A molecule's size limit depends on the input and output side of the reactor. A Standard Reactor has an input and output of 4 tiles by 4 tiles, while inside research reactors they are able to contain an output area of 4 tiles by 8 tiles.