Some of the most striking examples of iteroselective oligomerization are (i) the peptide synthesis controlled by the complex ribosome activity in biological organisms (Figure ) and (ii) the syntheses of oligomeric macrocycles such as cucurbiturils, calixarenes, or pillararenes which are, in some cases, templated by metal cations or solvent molecules to form iteroselectively a macrocycle of definite size (Figure for calixarenes). Note that, for n repeating units, the number of iterations i = (n -1) for linear oligomers but i = n for oligomeric macrocycles due to the additional iteration closing the macrocycle. For homo-polymerizations, the normal distribution would consist of a single polymer of maximum length (see Supporting Information), thus the normal ratio for any given length of polymer is essentially 0 and the ite is conveniently equal to the yield. For hetero-polymerizations, the normal distribution is more complex to calculate but some cases are covered in the Supporting Information.