A century ago, Hermann Staudinger
proposed the macromolecular theory of polymers, and now, as we enter
the second century of polymer science, we face a different set of
opportunities and challenges for the development of functional soft
matter. Indeed, many fundamental questions remain open, relating to
physical structures and mechanisms of phase transformations at the
molecular and nanoscale. In this Viewpoint, we describe efforts to
develop a dynamic, in situ microscopy tool suited
to the study of polymeric materials at the nanoscale that allows for
direct observation of discrete structures and processes in solution,
as a complement to light, neutron, and X-ray scattering methods. Liquid-phase
transmission electron microscopy (LPTEM) is a nascent in situ imaging technique for characterizing and examining solvated nanomaterials
in real time. Though still under development, LPTEM has been shown
to be capable of several modes of imaging: (1) imaging static solvated
materials analogous to cryo-TEM, (2) videography of nanomaterials
in motion, (3) observing solutions or nanomaterials undergoing physical
and chemical transformations, including synthesis, assembly, and phase
transitions, and (4) observing electron beam-induced chemical-materials
processes. Herein, we describe opportunities and limitations of LPTEM
for polymer science. We review the basic experimental platform of
LPTEM and describe the origin of electron beam effects that go hand
in hand with the imaging process. These electron beam effects cause
perturbation and damage to the sample and solvent that can manifest
as artefacts in images and videos. We describe sample-specific experimental
guidelines and outline approaches to mitigate, characterize, and quantify
beam damaging effects. Altogether, we seek to provide an overview
of this nascent field in the context of its potential to contribute
to the advancement of polymer science.