How to find axis and angle between two rotations.

I know Quaternion.Angle() finds the angle between two rotations, but how do I find the axis about which that angle can be applied?

If I understand what your looking for, this axis will be perpendicular to both Quaternions’ “LookAt” Vector3 (I think you’d use ToAngleAxis() axis output for that). If you get both those vectors, you can use the cross-product ( Vector3.Cross(V3,V3) ) of them to get a Vector3 perpendicular to both. I doubt this is the most efficient way though.