Tomato fruit growth relies on the process of endoreduplication, which leads to somatic polyploidy and cell expansion. This phenomenon is accompanied by significant nucleus modifications that affect transcriptional activity, nuclear size and morphology, including the formation of nuclear invaginations, which become deep and complex at high ploidy levels. Despite their extent, the structure and role of nuclear invaginations remain poorly understood in plants. Given the lack of nuclear invaginations correlates with altered endoreduplication in tomato mutants, the nuclear invaginations are supposed to play a key role in endoreduplication-driven growth. My PhD project aims 1) to characterize the structure of nuclear invagination according to endoreduplication levels using 3D immunofluorescence and CLEM correlative microscopy, 2) study the mechanical properties of invaginated nuclei through Atomic Force Microscopy (AFM), and 3) identify genes regulated at/by nuclear invaginations by combining RNAseq and CUT&RUN techniques. The expected results of this project will elucidate the roles of nuclear invaginations as mechanical and molecular hubs that boost endoreduplication and tomato growth.