Expansion microscopy: principles and uses in biological research

Many biological investigations require 3D imaging of cells or tissues with nanoscale spatial resolution. We recently discovered that preserved biological specimens can be physically expanded in an isotropic fashion through a chemical process. Expansion microscopy (ExM) allows nanoscale imaging of biological specimens with conventional microscopes, decrowds biomolecules in support of signal amplification and multiplexed readout chemistries, and makes specimens transparent. We review the principles of how ExM works, advances in the technology made by our group and others, and its applications throughout biology and medicine.NIH (Grants 1R01NS102727, 1R01EB024261, 1R41MH112318, 1R01MH110932, 1RM1HG008525, 1DP1NS087724)NSF (Grant 1734870)IARPA (Grant D16PC00008)US Army Research Laboratory & US Army Research Office (Contract W911NF1510548)US–Israel Binational Science Foundation (Grant 2014509

Imaging cellular ultrastructures using expansion microscopy (U-ExM)

Determining the structure and composition of macromolecular assemblies is a major challenge in biology. Here we describe ultrastructure expansion microscopy (U-ExM), an extension of expansion microscopy that allows the visualization of preserved ultrastructures by optical microscopy. This method allows for near-native expansion of diverse structures in vitro and in cells; when combined with super-resolution microscopy, it unveiled details of ultrastructural organization, such as centriolar chirality, that could otherwise be observed only by electron microscopy