Despite the separation of evolutionary lineages many hundred million years ago,/ncells of all eukaryotic organisms are structurally similar. Their control centre – the/nnucleus – contains most of the DNA of the cell and regulates the majority of cellular/nprocesses. DNA is packed in a small volume of the nucleus after interacting with/nnuclear proteins. These proteins facilitate DNA folding into a small space; participate/nin DNA replication, repair and transcription; and help to separate it from the/ncytoplasm. Additionally, these proteins have a strong impact on the function of the/ngenome. Indeed, the latter cannot be understood without a good knowledge of the/ncomposition, structure and behaviour of nuclear proteins, which are the most abundant/ncomponents of the nucleus (Sutherland et al. 2001). However, little information/nis available regarding plant nuclear proteins, except for histones and a few other/nproteins. We are only beginning to understand how the plant genome is organized/nand how it works. In this chapter, we summarize the current knowledge regarding/nthe plant nucleus and its protein composition, structure and function, with the aim/nof shedding light on the nature and function of vital components of plant cell nuclei.