In July I learned about atomic ordering in my alloys and how it may influence the martensitic start transition temperature. Strictly speaking depending on the chemical arrangement of atoms, occupation of lattice sites, there are three possible ordering variants. L21 representative of the Heusler structure in which all atoms in a ternary stoichiometric Heusler alloy X2YZ occupy their designated positions. This gives the full Heusler structure consisting of four interwoven fcc sub lattices. But in reality there is always some degree of chemical disorder influencing many of the physical properties of alloys. When X atoms stay ordered and disorder occurs between Y and Z atoms then we speak about a B2 structure. The third possibility arises when X and either Y or Z sites become disordered which leads to DO3 structure. The type of ordering obviously affects many of the properties as has already been said among them martensite start temperature. Therefore ordering may serve as tool for transition temperature control.