With the awareness that the Earth has a magnetic field, its mathematical description, discovery of remanent magnetisation in rocks and discovery of the periodic reversals of the geomagnetic field polarity, geomagnetism within geophysics became an interesting field of study. This is primarily due to advances in measurement technology and improved understanding of the magnetic field and its fluctuations in the geospace. Several important aspects of solid Earth geomagnetism are elaborated in the book. The first six chapters cover the basics of magnetism, magnetic minerals, biomagnetics, instrumentation and the behavior of geomagnetic field, while the rest of the book is devoted to practical applications with carefully selected examples and illustrations. Well-written and easy to read, the book vividly describes modern techniques in the subject matter covered, adequately supported by graphical explanations for complex mathematical concepts.