The notion of a causal process is introduced in this chapter, on which physical accounts of causation are based. First, Wesley Salmon’s mark transmission theory is described. After briefly pointing out some unclear elements of this theory, Phil Dowe’s conserved quantity theory is presented. What a causal process is depends on the conservation laws. This makes the conserved quantity account an empirical theory of causation, thereby allowing for a new way of clarifying overdetermination cases. I will suggest that adopting such an account can be regarded as implementing the fine-graining strategy in a way that is compatible with causal contextualism.