For the first time, in this book, a new view of metal-organic frameworks (MOFs) has been presented: MOFs with heterogeneous structures. In this field, there are different levels of understanding we need to consider. So, the principal aspects of heterogeneity that produce complexity in MOFs, their effects in the structure chemistry, performance and applications have been thoroughly reported. According to that there is no book that covers whole of the aspects of complexity in MOFs with heterogeneous structures, our findings can be as essential concepts with introducing complexity to design the new platforms of materials with advanced and better properties in the future.