While neuroscience has made enormous progress in understanding the brain, the implications of these empirical findings for ontological questions in philosophy including the mind–body problem remain yet unclear. In the first paper, I discussed the model of brain that as implied and supported by the empirical data. This leads me now to the question of an empirically plausible ontology of brain. Therefore, the aim in this second paper is the ontological characterization of the brain in terms of a process-based ontology that avoids what Whitehead described as "simple location" and "fallacy of misplaced concreteness". The discussion of the model of the brain is complemented by developing a process-based ontological characterization of the brain. Specifically, as based on Whitehead, I argue that "simple location" of the brain as thing or object in time and space amounts to nothing but an abstraction rendering what Whitehead described as "fallacy of misplaced concreteness". Instead of describing the brain as static, non-temporal and isolated thing or object, I characterize the brain ontologically by dynamic, temporal, and relational processes. This leads me to a process-based ontology of brain which may be specified in spatiotemporal terms. Since the world's larger spatiotemporal range or scale contains, e.g., nests, the smaller one of the brain, I characterize their ontological relationship by "spatiotemporal nestedness" and "spatiotemporal directedness". Such spatiotemporal relationship between world and brain precludes the confusion between the world as whole and the brain as part, e.g., "mereological confusion". I conclude that process-based or better, more specifically, spatiotemporal ontology of the brain and its relationship to the world may offer novel views on the question for the ontological relationship between mind and brain, e.g., the mind–brain problem, by converting or reformulating it as "world-brain problem".