The Lamin proteins are members of the intermediate filament protein family but are located inside the nucleus rather than in the cytoplasm (1). The lamins function as skeletal components tightly associated with the inner nuclear membrane. Originally the proteins of the nuclear cytoskeleton were named Lamin A, B and C, from top to bottom as visualized on SDS-PAGE gels. Subsequently, it was found that Lamins A and C were coded for by a single gene (2), while the Lamin B band may contain two proteins encoded by two genes now called Lamin B1 and Lamin B2. Lamin A has a mass of about 74 kDa while Lamin C is 65 kDa. The Lamin A protein includes a C-terminal segment of 98 amino acids missing from Lamin C, while Lamin C has a unique C-terminal 6 amino acid peptide not present in Lamin A. Apart from these regions Lamin A and C are identical so that antibodies raised against either protein are likely to cross react with the other. Lamin polymerization and depolymerization is regulated by phosphorylation by cyclin dependent protein kinase 1 (CDK1), the key component of “maturation promoting factor“, the central regulator of cell division. Activity of this kinase increases during cell division and is responsible for the breakdown of the nuclear lamina.