Oligomerization is a chemical process that links monomeric compounds (e.g., amino acids, nucleotides, or monosaccharides) to form dimers, trimers, tetramers, or longer chain molecules (oligomers). Examples are the conversion of nucleotides to oligonucleotides and amino acids to peptides. The boundary between what is considered an oligomer and a  polymer is unclear, but it is usually accepted to be in the range of 10–100 monomer units. Prebiotic experiments have shown that  activated nucleotides can be oligomerized using  clay minerals as catalyst.