The root structure is developing as well. It is far more dense than it was when it graduated to the bigger pot. No doubt this will continue until the pot is full of roots.
You can see that we’ve filled the 1 litre pot a little over half full. This is to encourage the roots to grow down and also to allow the top of the roots to have air around them. You don’t want to put too much water in the pot as access to air is important.