The interaction of DNA with various kinds of chemical components in a cell, such as proteins, lipids, and inorganic ions lead to the formation of DNA-colloid complexes and induces a conformation change in the DNA structure. In this relation, DNA is commonly found in vivo in higher concentrated or tightly packed states, for example in bacterial nucleotides, in chromatin, and in chromosomes, but an orderly collapsed DNA state can be produced also in vitro by addition of multivalent cations, such as polyamines. The general terminus for this compactisation is DNA condensation or coil-globule transition.

This review discusses the recent progress in our understanding of this phenomenon where the topics are among others DNA morphology, condensing agents, internal structure, mechanism of compactisation, theoretical models, and biological applications.