This book contains a comprehensive explanation of flame dynamic, thermal and chemical structures in lean and sub-lean combustions, which has not ever been reported before. The computational results has been experimentally proofed and interpreted in this book, which is almost impossible to be accomplished by any other method due to the difficulty and complexity of the combustion phenomena with the current available experiment equipment and/or technique. The programs of TECPLOT and Fortran are also included in the Appendix for reference.