The focus of this chapter is to discuss the properties and relevance of the mastic and mortar, also referred to as the fine aggregate matrix or FAM for short. Asphalt mastics and mortars can be regarded as the matrix in an asphalt mixture composite at an intermediate millimeter length scale. In practice, although mastics and mortars are almost never produced or used by themselves, they provide a convenient way to evaluate the influence of different types of binders, additives, modifiers, and mineral aggregates on the relative performance of different mixes. Mastics and mortars are also used to understand potential chemical and physicochemical interactions between the various component materials and the influence of factors such as aging and moisture. This chapter discusses the role of fillers in mastics from a mechanical and physicochemical perspective. This chapter also briefly presents typical approaches to use mortars as a means to evaluate the relative performance of various materials.