If it is not cracked then it is not working. This statement is the actual result of difference between tension strength of concrete and tension strength of steel in concrete structures elements that are economically designed. In spite of that, engineers rarely use this statement to explain cracks in buildings, but sometimes they use it to calm down the owner of some cracked building. That's why we should define acceptable cracks and their degrees. Cracks in concrete and reinforced concrete structures are a bad sign, although some of these cracks have no negative effect on the utilization of the structure. Reasons of cracks are various and different, some of them might occur in different types of cracking while others may lead to a single type of crack. Cracks formation in concrete varies due to the different factors causing them, which also may be structural or related to the utilization of building. It is not easy to put a useful list for probable reasons of cracking as cracks have many shapes and any one of them might increase the danger of another one or even exceeds it. To explain the relationship between these types, we proposed the cracking tree, which may help the designer to take into consideration the probable reasons for cracking. The main specification of cracks is that its three nodes define the three periods in the life of a structure: design, construction and service. These are also divided into lists including reasons causing cracking and their effects on each other. Cracking tree branches into tension roots, taking into consideration that the first branches determine the physical properties of cracks (width, depth, length,…). Then these branches take their way throughout the three phases,(restriction of movement is the most important branch). When these branches stop growing, they can tell the severity of cracking, in respect to durability and beauty. This definitely still needs accurate study and repair. This research aims to study the direct reasons of cracking, factors that increase cracks, and types of cracking growing in structural members (Columns, Beams, Plates,..). Add to that the procedures needed to prevent or stop cracks growing. We also offer an attempt to point the best methods and materials to be used for restoration.