A small comment to start with: to be on board the International Space Station is in a way like living in a dream. You are walking close to the edge of the technological horizon for our generation. It is extremely motivating and it is an honour to be here as a European and an Italian. It is challenging and full of rewarding situations, but it is not easy.
We have hundreds, maybe thousands of items stored everywhere inside the Station. It is as if by magic that the crew, with the help of people on the ground, can track down almost anything. This is all credit to a lot of effort and dedication on both sides to record the location of each item in a database.
At the same time it can be very difficult to organise your work on board. Can you imagine setting up an experiment when everything is floating? You have to restrain yourself, as well as all the items you need, and your equipment... and by the way; free space is really almost non-existent.
It is amazing sometimes to think about the way we work. One day all 5 of us were in a single module, the Service Module. Sergei and Sasha were working on a medical experiment, Leroy was training on the treadmill, John was eating a snack, and myself working on the ESA experiments. You soon adapt and learn to move, think and plan tri-dimensionally.
Yes, in fact on board you are using all the tri-dimensional space, without making a real distinction between the floor, ceiling, and the walls. Although in truth there is a difference, and we all prefer to work in the upright orientation, like on the ground. But if the need arises, we can practice our spider skills and make perfect use of all available space.