In a living cell, multiple proteins, DNAs and RNAs work as macromolecular complexes. Among them, chromatin is involved in packaging a huge amount of genomic DNA into the nucleus. Chromatin plays an important role in epigenetic gene regulation, independently of genomic DNA sequence. Additionally, it is known that crucial nuclear events, such as transcription, replication, and repair occur in the chromatin. Our lab focuses on understanding the chromatin structure and function in particular using cryo-electron microscopy, which is a powerful tool for recent structural biology. Our strategy for chromatin study is based on structural and biochemical analyses using an in vitro reconstituted chromatin, chromatin isolated from the nucleus and in situ chromatin. We have tackled using both single particle cryo-electron microscopy and cryo-electron tomography to unveil nuclear event regulated by various chromatin structure.