The accurate charge density studies by the Maximum Entropy Method (MEM) utilizing X-ray diffraction is outlined with some examples. The basic concept of the method is stated in some details. In addition, some experimental charge densities are given to demonstrate the usefulness of the method, such as endohedral metallofullerenes, metal hydride and intermetallic compounds. In La₂@C₈₀ metallofullerene case, the extraordinary charge density distribution is revealed, that is two La atoms form pentagonal dodecahedron charge density due to the hopping motion inside fullerene cage. In MgH₂ metal hydride case, charge density peaks of hydrogen atoms are clearly found in MEM charge density map, whereas no such charge density peaks are found in direct Fourier charge density map.