In the US, 100' is the defacto minimum altitude, because you can descend to 100' above the TDZE if you have the approach lights in sight, and you can almost always see them from 200' directly above, especially in the dark. I did this the other night on a medevac flight, with home reporting 1/4 mile vis and 100' VV. We got the approach lights in sight at 200', the runway end lights at 100', and landed legally. No special training or authorization is needed for this. Other national regulations may be different.