Investigation of the molecular basis of a complex biological system, such as the brain, can lead to fundamental understanding of its composition and function, and to a new strategy to repair it. Such investigation, however, requires a tool that can capture biological structures and their molecular constituents across multiple orders of magnitude—from nanometers to centimeters—in length. Electron microscopy offers nanoscopic resolution but lacks molecular information to differentiate endogenous biomolecules as well as imaging speed to cover millimeter-scale specimens. Light microscopy provides molecular contrast but is limited by optical diffraction and the tradeoff between imaging speed and photobleaching.

In this talk, I will first introduce an optical imaging pipeline named expansion lattice light-sheet microscopy (ExLLSM) and its application to multiplexed, volumetric imaging of molecular constituents in cells and intact tissues. Using ExLLSM, our study has revealed molecular-specific structures of organelles, synapses, myelin sheaths, and neurites in rodent and insect brains at ∼60 by 60 by 90 nm effective resolution across dimensions that span millimeters. Next, I will present two recently developed methods that further extend the resolution and throughput of ExLLSM: (1) a non-radical hydrogel chemistry that forms a homogenous polymer network and physically separates biomolecules or fluorescent labels up to 40-fold linearly, and (2) a multi-modal optical microscopy that enables rapid, high-resolution imaging of both expanded and live tissues. Lastly, I will discuss the significance of these imaging methods in the context of microanatomy and functional omics.