Abstract: Compositions and methods for preparing and using a swellable polymer network for expansion microscopy (ExM) applications. The swellable polymer network can be prepared on demand using external stimuli for ExM applications. A variety of external stimuli can be employed, including light irradiation, pH, temperature, and magnetic fields. Network preparation using light irradiation is particularly advantageous, as it allows tuned control over the network properties through the variation of time and dose of light irradiation. In other words, light irradiation can be employed with a wavelength and intensity that enables a polymer network formation.