The DNA inside the cells is packaged in the form of chromatin with the help of proteins and assumes dynamic structures. The two important aspects of chromatin which are the supercoiling and nucleosomes are studied in the thesis, primarily using nanopore technique. Firstly, we studied the branched structures on the supercoiled DNA with high-resolution and also studied its enzymatic conversion to linear DNA. Then we extended our studies to probe the stability of DNA-protein complexes, particularly in the case of nucleosomes. Upon application of forces, we observed the breakdown of nucleosome structures in case of both the isolated nucleosomes and nucleosome arrays into smaller less-stable structures that are detected and quantified. The interpretation of various biologically relevant structures from the nanopore-generated electrical signatures would be discussed in detail. In summary, this thesis work informed us of the huge heterogeneity in the structures that is possible at the level of DNA and DNA-protein complexes.