We learn about developments in 20th-century theoretical inorganic chemistry, starting with coordination complexes as explained by Christian Blomstrand, Sophus Jørgensen, and Alfred Werner. Theory from a quantum-chemical perspective began with Jean Becquerel and Hans Bethe and "Crystal Field Theory." We then look at John Griffith and Leslie Orgel's "Ligand Field Theory." From classical complexes and their multitude of shapes, we move to organometallic complexes and bioinorganic complexes. The last topic of the episode is the discovery of ferrocene in 1951, and the weird shape the molecule has.