Delivery of chemotherapeutic agents to the nucleus of the cell can dramatically increase the efficacy of cancer therapy due to the vital role of the nuclear material in cell replication. However, due to the complexity in the control of the synthesis of nanocarriers able to cross the nuclear barrier, and the challenges in tracking small particles with spatio-temporal resolution, the reasons behind differences in nuclear internalization of nanoparticles are not yet fully understood. Previous studies have reported particles characteristics (e.g. size, aspect ratio, elasticity, material) and heterogeneity in response from different cell types as possible causes of this discrepancy. In this thesis, it has been combined a fluorescent based approach, namely pair correlation microscopy, with 18 nm and 10 nm fluorescent silica nanoparticles to track movement and translocation of nanoparticles into the nucleus of migrating versus no-migrating MCF-7 human breast cancer cell line. Initially, by using the 18 nm Cy5 labelled fluorescent silica nanoparticles, it was found that behaviour of nanoparticles internalization into the nucleus of MCF-7 breast cancer cell linepresented heterogeneity in internalization.In particular, two cases, consisting of particles being able to enter the nucleus and particles stopped at the nuclear envelope, were identified. To further investigate any biophysical reasons behind this discrepancy, 10 nm Cy5 labelled silica nanoparticles were employed. It was found that, due to chromatin rearrangement during cell migration, the quantity of internalized nanoparticles into the nucleus of isolated single cells increases compared to non-migrating cells. Furthermore, after the cell stops the migration, chromatin unfolds, and the particles internalized are ejected from the nucleus. Chromatin organization inside the nucleus has been widely studied due to its importance in the genetic and epigenetic expression, yet its conformation and dynamics in living cells is not well understood. Herein, is reported a measurement technique which combines fluorescent correlation microscopy with a nanoparticle system to probe the spatio-temporal organization of higher order chromatin structure in living cells and to correlate its conformation and dynamics with a specific cell activity, particularly migration. Measurements of chromatin occupied surface area, evaluated at the focal plane, within the nuclear space during migration reveals less condensed chromatin compared with cells on the quiescent state. Furthermore, by using an intercalator to directly visualize the chromatin, the volumetric chromatin occupancy inside the nucleus was mapped. The technique, called nuclear volume analyzer, uses a custom developed Matlab code that divided the nucleus into voxels, extract the percentage of chromatin presents in that voxel, and reconstruct chromatin real time conformation in three dimensions by using a 3D renderer. The results reported in this thesis demonstrate the role chromatin exerts in particles translocation into the nucleus and their residence time within the nuclear space, showing that changes in the folding of the chromatin serves to influence the influx and efflux of nanoparticles from the nucleus. Together, these findings give new insights on the nuclear translocation process of nanoparticles and reveals one of the possible biophysical reasons behind the discrepancies in nuclear uptake previously reported in literature. These findings may facilitate the design of new smart nano-delivery systems able to target migrating cells, in cancer metastasis and/or angiogenetic processes, with a possibly net increase in the efficacy of payload release directly in the nucleus. Finally, the combination of the correlation microscopy and the nuclear volume analyzer techniques allow the simultaneous quantification of the dynamic of chromatin condensation in the nuclei of living cells and gives 2D and 3D information about chromatin dynamics and distribution.