Mohammed Yusuf, Bo Chen and Ian Robinson
The higher order structure of human chromosomes remains to be elucidated, the 30 nm mystery is still not solved. Transmission electron microscopy (TEM) cannot be used to determine the internal structure because the chromosomes are too thick (about 1.4 micrometers) and scanning electron microscopy (SEM) is a surface imaging technique. For this purpose, three-dimensional (3D) serial block surface scanning electron microscopy (SBFSEM) was used for the first time to image mitotic human chromosomes [1].