Nanoscale imaging of biological systems via expansion and super-resolution microscopy

Super-resolution microscopy (SRM) has revolutionized life sciences by overcoming the diffraction limit, enabling the visualization of biological structures at the nanoscale. Expansion Microscopy (ExM) has emerged as a powerful and accessible technique that enhances resolution by physically enlarging the specimen. Importantly, the principles of ExM provide a unique foundation for combinations with SRM methods, pushing the boundaries of achievable resolution. This review explores the fundamental principles of ExM and examines its successful integration with various SRM techniques, including fluorescence fluctuation-based SRM, structured illumination microscopy, stimulated emission depletion microscopy, and single-molecule localization microscopy. We discuss the applications, strengths, limitations, and resolutions achieved by these combined approaches, providing a comprehensive guide for researchers to select the most suitable method for their specific scientific needs. Key considerations when combining ExM with SRM include the impact on fluorophores, the requirement for specialized buffers, and the challenges posed by the sensitivity of expanded hydrogels to temperature and hydration. Strategies to address these challenges, such as optimized labeling techniques and gel re-embedding, are discussed in detail. This review aims to assist researchers in navigating the rapidly evolving landscape of ExM and SRM, facilitating the development of tailored imaging pipelines to advance our understanding of biological systems at the nanoscale.