Werner's coordination theory refers to coordination complex's. A coordination complex is an atom or ion (usually metallic) bound to a surrounding array of molecules.

Complex species are complex coordination molecules havin a coordination centre, frequently a metal.
Neutral species are substances without electrical charge.

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The total response of an organism is often complex, involving several parts of the body. For this to occur, some kind of coordination is required.

The light blue color of a solution of CuSO4 in water is due to absorption of yellow light by a coordination complex of water and copper cations. When NH3 is added, the water molecules in the coordination complex are replaced by ammonia molecules, and the resulting complex absorbs yellow light more strongly than the original one.