What the biological mesoscale range is and outline what types of structures it includes?
The biological mesoscale range includes biological structures that range from 10 to 100 nanometers (billionths of a meter). Structures in this size range include viruses, cellular organelles, large molecular complexes, and any other internal cellular environments within that range.
The cell is a hierarchy of structures that span from atoms to organelles, all of which interact in an intricate choreography with tempos that range from femtoseconds to hours. The mesoscale is important because it represents the range of scales of cellular systems that are not fully accessible to a single experimental technique.
Why has it been difficult to visualise structures in this range, when scientists have been able to study both larger and smaller biological structures, such as cells and proteins respectively?
The real problem is not visualizing isolated component structures but rather visualizing the complex molecular environment of these component structures as they exist in a living cell. Atomic level structures of large molecular assemblies such as the ribosome are within this mesoscale range and have been visualized with x-ray crystallography, but in isolation. Larger cellular structures such as organelles are also within this range and can be visualized with electron or even light microscopy, but not at the atomic level. Unfortunately there does not exist a single experimental technique that can visualize the 3 dimensional structure of cellular environments at the molecular scale