All the important biomacromolecules in cells are formed by the polymerization of small molecular monomers. Polymerization within cellular microenvironment is very common and important in cell metabolism. Thus

transfer of polymerization reactions from laboratory flasks to cellular microenvironment is expected to be a powerful and versatile tool for regulation of cellular function. Owing to the diversity and tunability of polymers

in situ

polymerization in cellular microenvironment may bring great possibilities for understanding

analysis and regulation of cellular function

which has great potential in the field of biomedicine. In this review

we summarize and classify

in situ

polymerization triggered by exogenous or endogenous stimuli (such as light

glutathione

reactive oxygen species

enzymes

etc

.) in the cell microenvironment. The applications of

in situ

polymerization in the field of antitumor therapy

nerve repair and antimicrobe are briefly introduced. Finally

the key challenges of

in situ

polymerization in organisms are discussed

and its future development is proposed.