I have a sphere with a particle system added to it: Add modifier - Particle system. In its preferences, I set it to Hair, with Render as Object (set to a cube object) and some other details like scale, rotation, etc.

As you can see below, this makes the cubes be distributed on the surface of the now transparent sphere. I would like to have the cubes emitted inside the sphere. Is this possible?

Just in case this would be possible with another modifier/approach: I need to have randomized sizes and rotation of the cubes and need to have 1 or 2 thousand of them.

I have a sphere with a particle system added to it: Add modifier - Particle system. In its preferences, I set it to Hair, with Render as Object (set to a cube object) and some other details like scale, rotation, etc.

As you can see below, this makes the cubes be distributed on the surface of the now transparent sphere. I would like to have the cubes emitted inside the sphere - not just below the surface, the sphere should be filled with cubes. Is this possible?

Just in case this would be possible with another modifier/approach: I need to have randomized sizes and rotation of the cubes and need to have 1 or 2 thousand of them.