We usually consider the human genome as a linear sequence of letters (the nucleotides). These form a book (the DNA molecule) and encode the information that determines the appearance and
functions of our body.
For example, specific combinations of nucleotides form the genes, that contain the information to produce the different proteins. The latter perform several functions in the cells. Some proteins are the building blocks of the cells, e.g. the collagen fibers or the keratin, and others (the enzymes) are the machines to perform the different reactions inside the cell. Other DNA sequences represent, instead, instructions for assembly or regulation of mobile activities. Just as all the books we know are written on paper or digital pages, our DNA also needs support to be stored and correctly used by the cell.

The knowledge of the structure of this support is as important as knowing the content of the sequence itself. Think, for example, of preparing your favorite dish. You open the recipe book but
discover that the page you are looking for has been removed or got stuck to the next one. The result is equivalent to not having the text of the recipe. You cannot read it and, more importantly, you
cannot enjoy your favorite dish.

Similarly, the genome is hosted into very complex structures (chromosomes) in the cell nucleus. Their foldings in space are essential to allow the cell to read all the instructions necessary for its
proper functioning. In some circumstances where the structure of chromosomes is damaged, cells cannot function properly and contribute to fatal diseases such as various types of cancer or
developmental disorders.