The superconductivity of MgB2 has been hidden for nearly 50 years although it has the highest Tc among the intermetallics superconductors. Beside the high Tc, simple crystal structure, large coherence length, high critical field, transparency of grain boundaries to current flow and low normal state resistivity MgB2 is a fascinating topic to study for both large scale application and electronic devices. Moreover, the presence of two-gap superconductivity (ð and ó band) has been theoretically and experimentally established. However, critical current density of pristine MgB2 drops rapidly in the high magnetic field due to the weak pinning centres and low upper critical field. During the past three years, novel techniques and developments for fabrication of useable MgB2 have been reported, including chemical alloying, irradiation, thermo-mechanical processing techniques and magnetic shielding to improve the critical density, upper critical field and the irreversibility field. Among the studies, atomic substitution, especially using nano-particles, may help in clarification of the superconductivity mechanism thus making it appropriate for practical application. On the other hand, the momentum of enhancing flux pinning using chemical doping is moving to a positive side. Nano-SiC powder is well known for effective improvement of the critical current density. In this book, a brief introduction of superconductivity in MgB2 is introduced. Further, the basic electronic and magnetic properties of the MgB2 as well as its crystal structure are reviewed. The authors also discuss the preparation method that has been well developed for experimentation on MgB2. Along with that, they review the experimental results of the chemical alloying on MgB2, particularly on the critical current density. In addition, the future prospects of MgB2 and developments for applications in the current superconductivity market are given.