Book excerpt: The historical background of the development and utility of ferrites. The development of spinel ferrites, the various theories relating to magnetic behavior and electric conduction are discussed in detail. The theory of ferrite nanoparticles is given with special reference to nanoscience and nanotechnology. The development of NiCuZn ferrites, the importance of the ferrite system which is chosen for the stiochiometry is discussed. The best suited method of synthesis which is sol-gel autocombustion method is discussed in detail. Literature survey with special reference to the study of divalent and trivalent substitution is also undertaken. The objectives of the present investigative work and the various characterizations which are chosen for the study are discussed. The conventional method of synthesis is ceramic method, which has disadvantages, the chemical sol-gel autocombustion method which is more advantageous is chosen for the investigations. The suitable chelating agent employed is glycine which has high negative heat of combustion (-3.24 kcal/gm).The working principles of various instrumentations like XRD, FTIR, Raman spectrometer, EDAX, SEM, TEM, VSM etc are explained in detail. The instrument specifications are given for each type. The divalent Mg2+ and Co2+ ion substitution in NiCuZn ferrites and the associated structural, optical, magnetic and electrical properties are recorded. The effect of rare earth Tb3+ and Dy3+ ion substitution on NiCuZn ferrites is also discussed.