Light is shining and beautiful as well as being a mystery for many hundreds of centuries. But, after separation, into its components, using a prism, a very beautiful rainbow appears. A lot of natural events around us are composed of unknown natural sources, while we just observe the results of these sources. Theses phenomenon include a wide range from genomes to multiuser communications signals. Blind Source Separation (BSS) extracts those original sources and discovers structural components of the fundamental phenomenon involved. BSS does not need apriori knowledge of the mixing process or the sources. Indeed BSS blindly separates the mixed sources. Such ability makes BSS a exible and powerful framework for employment in a wide range of applications. BSS is now one of the hottest and emerging areas in Signal and Image Processing, and it has drawn researchers attention in different areas, like biomedical engineering, medical imaging, speech processing, communication systems and etc. This book presents an explanation to BSS methods, calls on the reader's intuition and it simply applies BSS over Speech, Image and MIMO OFDM communications.