Plasma Physics is itself the physics of complex system. The thermal de Broglie waves of neighboring particles overlap and thus give rise to quantum phenomenon. Such quantum effects in plasma make it further complex. The effects become important in many environments such as astrophysical plasma, neutron star, biophotonics, laser produced plasma, ultra small electronic devices, metal nano-structures etc. The free electrons in metal can be better modeled by using plasma concept. In this connection the study of electron plasma waves becomes important. Using quantum hydrodynamic (QHD) model the modulational instability is studied in quantum plasmas including relativistic effects. The purpose of this book is to study the amplitude modulation and formation of envelope soliton in different configuration of quantum plasma. There is huge scope to explore the quantum properties in ultra dense plasmas. This book is an attempt towards it. Hope the reader will be able to find the physics of quantum plasma interesting.