To understand and to evaluate or predict soil behaviour, one needs to have information on the properties of the soil under consideration. The properties of a particular soil are dependent on the nature of the soil, that is, its composition and how its various soil fractions interact with each other to provide the soil its intrinsic properties and attributes. Actions from environmental forces and human activities will impact the nature of a soil directly. These impacts will change the nature of a particular soil and can be anticipated with knowledge of the nature of the soil and the nature of the impacts. The various elements that combine to establish the nature of a soil and its properties are discussed in this chapter.