The striations result from the fact that the thick and thin filaments have different refractive indices in the light microscope. The myofibrils are also birefringent. The dark bands in the micrograph represent regions of overlap between the thin and thick filaments. The Z-line which ties the thin filaments together can also be seen. Two sarcomeres, or sets of filament arrays, shortening according to the filament sliding hypothesis Scientists have a tendency to break down organized systems into ever smaller parts, in the hope of better understanding how they work.
Muscle is no exception.
Sophisticated electron microscopy is used extensively, as well as x-ray diffraction. Low angle x-ray diffraction makes use of the regular packing of the proteins in muscle to diffract electrons in a regular pattern, thus revealing the molecular organization of the proteins, and more importantly, providing the opportunity to see the proteins move. The advantage of X-ray diffraction is that live, contracting muscles or muscle fibres can be used, rather than fixed and sectioned tissue. It is a method which provides information at the molecular level without the need to break down the organ to minute fractions. With synchrotron radiation, it is possible to obtain information with a time resolution in the tens of microsecond range.