A beacon b∈Rd is a point-shaped object in d-dimensional space that can exert a magnetic pull on any other point-shaped object p∈Rd. This object p then moves greedily towards b. The motion stops when p gets stuck at an obstacle or when p reaches b. By placing beacons inside a d-dimensional polyhedron P, we can implement a scheme to route point-shaped objects between any two locations in P. We can also place beacons to guard P, which means that any point-shaped object in P can reach at least one activated beacon.The notion of beacon-based routing and guarding was introduced in 2011 by Biro et al. [FWCG'11]. The two-dimensional setting is discussed in great detail in Biro's 2013 PhD thesis [SUNY-SB'13].Here, we consider combinatorial aspects of beacon routing in three dimensions. We show that ⌊(m+1)/3⌋ beacons are always sufficient and sometimes necessary to route between any two points in a given polyhedron P, where m is the smallest size of a tetrahedral decomposition of P. This is one of the first results to show that beacon routing is also possible in higher dimensions.