Imaging of Hydrated and Living Cells in Transmission Electron Microscope: Summary, Challenges, and Perspectives.

Transmission electron microscopy (TEM) is well-known for performing in situ studies in the nanoscale. Hence, scientists took this opportunity to explore the subtle processes occurring in living organisms. Nevertheless, such observations are complex─they require delicate samples kept in the liquid phase, low electron dose, and proper cell viability verification methods. Despite being highly demanding, so-called "live-cell" experiments have seen some degree of success. The presented review consists of an exhaustive literature review on reported "live-cell" studies and associated subjects, including liquid phase imaging, electron radiation interactions with liquids, and methods for cell viability testing. The challenges of modern, reliable research on living organisms are widely explained and discussed, and future perspectives for developing these techniques are presented.