The invention provides a method for preparing an expanded renal (kidney) tissue sample suitable for microscopic analysis. Expanding the kidney sample can be achieved by binding, e.g., anchoring, key biomolecules to a polymer network and swelling, or expanding, the polymer network, thereby moving the biomolecules apart as further described herein. As the biomolecules are anchored to the polymer network, isotropic expansion of the polymer network retains the spatial orientation of the biomolecules resulting in an expanded, or enlarged, kidney sample.