Whether for separation processes, photovoltaics, catalysis, or electronics, porous polymer membranes are needed in many fields. Membranes with micropores that switch between different shapes and/or sizes would expand the possibilities. In the journal Angewandte Chemie, scientists have introduced a process that produces porous films made from shape memory polymers with precise dimensions. The shape and size of the pores can be reversibly changed with light. No mechanical deformation is needed.