In the past two decades we have witnessed the impact of femtochemistry that probes time-dependent electronic or vibrational transition energies of chemical species in ultrafast reactions with the atomistic time resolution of femtoseconds. However, the spectroscopic information attained is indirect and intuitive structural information of transient species has been the subject of frontier researches in the new millennium.

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The recent emergence of 4D electron microscopy, which uniquely combines the ultrafast time resolution of femtochemistry and ultrafine spatial resolution of TEM, has opened a new era for direct visualization of atomic and molecular motions of matter. Yet, because of limited function, observations have been made to periodic (crystalline) atomic and molecular architectures and non-periodic (amorphous) objects of hundreds nanometers or bigger. In the ULSaN lab, we develop an advanced ultrafast electron microscope with invulnerable capabilities that can circumvent present limitations and promote the new methodology to a powerful platform to directly image molecular and collective motions, dissect fundamental phenomena, and deliver new concepts for specific control and global function of matter.

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