Review of 4Pi Fluorescence Nanoscopy
Xiang Hao, Yiming Li, Shuang Fu, Yanghui Li, Yingke Xu, Cuifang Kuang, Xü Liu
Abstract
Since the 1990s, continuous technical and scientific advances have defied the diffraction limit in microscopy and enabled three-dimensional (3D) super-resolution imaging. An important milestone in this pursuit is the coherent utilization of two opposing objectives (4Pi geometry) and its combination with super-resolution microscopy. Herein, we review the recent progress in 4Pi nanoscopy, which provides a 3D, non-invasive, diffraction-unlimited, and isotropic resolution in transparent samples. This review includes both the targeted and stochastic switching modalities of 4Pi nanoscopy. The schematics, principles, applications, and future potential of 4Pi nanoscopy are discussed in detail.