# Label‐free imaging of intracellular structures in living mammalian cells via external apodization phase‐contrast microscopy

## TL;DR

This paper introduces a new microscopy technique that allows scientists to see inside living cells without using labels, offering detailed views of cellular structures and their changes over time.

## Contribution

The novel contribution is the development and application of label-free external apodized phase-contrast (ExAPC) microscopy for high-resolution imaging of intracellular structures.

## Key findings

- ExAPC microscopy enables label-free imaging of intracellular structures with high spatiotemporal resolution.
- Quantitative analysis using ExAPC and fluorescence microscopy reveals heterogeneities in biomolecular condensates, lipid droplets, and mitochondria.

## Abstract

Developing techniques to visualize intracellular structures, which influence the spatiotemporal functionality of biomolecules, is essential for elucidating mechanisms governing cellular behavior. In this study, we demonstrate that label‐free external apodized phase‐contrast (ExAPC) microscopy serves as a valuable tool for the simultaneous observation of various intracellular structures with high spatiotemporal resolution, while successfully mitigating halo artifacts. Additionally, through quantitative analysis of images obtained by combining ExAPC microscopy with fluorescence microscopy, we identified distinct heterogeneities in biomolecular condensates, lipid droplets, and mitochondria. Our findings highlight the potential of ExAPC microscopy to provide detailed insights into alterations in intracellular structures associated with diverse cellular processes, corroborating the existing knowledge and potentially contributing to the discovery of previously unknown cellular mechanisms.

Advanced techniques to visualize the spatiotemporal functionality of biomolecules are essential for elucidating mechanisms governing cellular behavior. External apodization phase‐contrast (ExAPC) microscopy enables label‐free visualization of diverse intracellular structures in living mammalian cells. By enhancing phase‐contrast imaging through optical apodization, ExAPC reveals fine subcellular details, such as lipid droplets and organelle contacts, without fluorescent labels. This method provides a powerful, non‐invasive tool to study cellular organization and dynamics, supporting broad applications in cell biology and biomedical research.