It contains energetic molecular crystals, energetic ionic crystals, energetic atomic crystals, energetic metallic crystals and energetic mixed-type crystals and the substructures closest to crystal packing. Meanwhile, the common intermolecular interactions in energetic crystals will be introduced. In addition, theoretical and simulation methods for treating the intrinsic structures will be briefed, as they are the main tools to reveal the molecules and crystals. Besides, the polymorphism as a level of intrinsic structures will be briefly discussed. In the final of this book, we introduce the crystal engineering of energetic materials. This book features the first proposal of intrinsic structure and crystal engineering of energetic materials and the understanding of the properties and performances of energetic materials by maintaining a concept that structure determines property. It helps to promote the rationality in creating new energetic materials, rather than increase experience.