Mereotopology is today regarded as a major tool for formal-ontological analysis, and for many good reasons. It is highly general and highly domain independent. It is ontologically neutral, treating all entities as individuals, as entities of the lowest logical type. Mereotopology is built up out of mereology together with a topological component, thereby allowing the formulation of ontological laws pertaining to the boundaries and interiors of wholes, to relations of contact and connectedness, to the concepts of surface, point, neighbourhood, and so on. Mereotopology faces problems when its methods are extended to deal with time and change.