Neutrons can see hydrogen (deuterium) atom structurally and dynamically. The specific feature makes neutrons unique method for biological science. Neutron protein crystallography enables to identify hydrogen atom positions, which leads to the understanding of hydrogen bond network around the active site. One successful example is the discovery of the low barrier hydrogen bond in photoactive yellow protein. Recent advances in incoherent scattering enable to distinguish hydration water dynamics from protein dynamics. The construction of neutron dynamic data base is now discussing. Although criticism against the usefulness of neutrons in biology has been raised, we should be confident that neutron can contribute to the progress of biological science substantially.