“…Expansion Microscopy (ExM) (Chen et al, 2015; Gallagher and Zhao, 2021), which physically expands tissue samples ∼4 to 20-fold by embedding them in swellable hydrogels, has resolved subcellular protein distributions of synaptic targets in mouse brain tissue (Chen et al, 2015; Tillberg et al, 2016; Ku et al, 2016; Chozinski et al, 2016; Chang et al, 2017; Murakami et al, 2018; Truckenbrodt et al, 2019; Park et al, 2019; Shen et al, 2020; Campbell et al, 2021; Gao et al, 2021; Park et al, 2021; Damstra et al, 2022), as well as map RNA transcripts within axons and dendrites in the brain (Alon et al, 2021). However, while the expansion-related decrowding avoids fluorescence quenching, ExM has traditionally capitalized almost exclusively on antibody labelings, and no ExM method has demonstrated correlative molecular and contextual imaging with synaptic resolution so far.…”