Raman imaging of molecular groups in the wavenumber silent region.

Raman imaging in the wavenumber silent region emerged around 15 years ago as a powerful tool for visualizing biomolecules and synthetic compounds in complex environments with minimal spectral and biological interference. Since then, the field has advanced from simple proof-of-concept studies using available tags to the rational design of highly efficient Raman labels with sharp silent region signatures, now applied to real biological and biomedical questions. This review traces the evolution from the versatility of label-free Raman to the increasing relevance of labeled strategies, emphasizing how tag design influences functionality, application, and impact. We highlight recent progress in both the synthesis and deployment of tags tailored for specific cellular targets and processes and discuss the emerging need for labeled strategies to meet the demands of sensitivity, multiplexing, and biocompatibility in complex systems. Through this design-to-application perspective, the review provides a comprehensive overview of the current capabilities and significant applications, and identifies key future directions to fully exploit the potential of silent region Raman imaging.