Volumetric Nebula Generation ?

Hey everyone,

I have been looking into Raymarching for generating a volumetric nebula cluster that can be navigated through, but so far the solutions have not been looking very realistic. I am looking forward to make something like the video shown below :

Let me know how should I approach in developing something like this.

Below is my previous work on Volumetrics using Raymarching technique, but that is not even close to what I have been thinking of making.