  The electromagnetic hopfion (EM hopfion) is a topologically nontrivial
solution to the vacuum Maxwell equations with the property that any two field
lines belonging to either the electric, magnetic, or Poynting vector fields
(EBS fields) are closed and linked exactly once. The most striking and
characteristic feature of this peculiar field configuration is the existence of
an exceptional constant-time hyperplane wherein the EBS fields are tangent to
three orthogonal Hopf fibrations. Using twistor methods we find the spin-$N$
generalization of the EM hopfion. Furthermore, we analyze the spin-2 solution
within the framework of gravito-electromagnetism and show that the topology is
manifest in the tendex and vortex lines. By decomposing the spin-2 field into
spatial gravito-electric and gravito-magnetic tensors, we characterize its
topological structure and evolution in terms of the EM hopfion.
