The master thesis of Johanna Maria Ticar reveals high-resolution insights into the myocardial microstructure and illustrates that cardiac muscle fibers are straight, running in parallel with one preferred fiber direction, however, deposits such as fat seem to compromise the regular and compact structure. Second harmonic generation imaging combined with optical tissue clearing is an accurate method for determining the three-dimensional muscle fiber and sheet orientations and hence, allows the calculation of fiber rotation throughout the ventricle wall.