How to recover work output from past lab when the head is uncooperative? I have done a part of my PhD project in the lab that was not in our university and in another city. At the end of my work I produced a mutant enzyme that was necessary to perform another experiment to measure one of its characteristics. but they did not have the facility. So, the head of that lab told me that they would send my samples for the measurement to one  of their collaborator. I left their lab and returned to my city to continue my project. After that, whenever I followed up about the measurement the head of that lab postponed sending the samples to another time. After Six months I have asked him to send my samples to the lab that I introduced him. But,... He did not. It is almost two years but they did not send my samples for the measurement. Once I complained about this issue to him, he replied that whatever produced in his lab "is exclusively him". Is my samples really exclusively him? It was my idea and my work. How can I handle that? Is there any place that we can complain about these kind of issues?
If an artist borrows a canvas and a brush to create a beautiful piece of art, who owns the art? The person owning the canvas or the artist himself? Who owns the intellectual property (IP)?

Your problem is a very ethical question and I would expect that there are laws and agreements between your university and the guest university governing that. If your University or Faculty has a dedicated law department I suggest you get in touch to figure out what regulations apply to your specific case; Asking "who owns what".

You should escalate this issue to higher levels: Supervisor, Head of Department, Devision, Faculty, [...] There are people with enough power and knowledge to deal with this issue in the correct way. You are not the first person to face such an issue; You will not be the last =) In fact you should have done so 1.5 years ago.

I am no lawyer, so I suggest you speak to somebody more qualified (and local). As a rule of thumb, IP belongs to the person that pays for the work. 

If your guest professor contracted you he owns it and there isn't much you can do. 

'produced in his lab "is exclusively him" ' is not enough to claim IP as that is merely providing the tools [at least in computer science]. That's saying "I gave Picasso his brush and he painted this in my Café, I own that painting".

In your case you are using his hotbed, ... "Consumables" (e.g. the paint and the canvas) are again different. There it very much depends on local regulations and there could be a caltrop hidden somewhere. Again speak to local people with more experience, in my experience they are more then happy to help.

Now above is something you can do. The consequence is that it will ruin the relationship between your two labs (plus some potential other consequences). On the other hand you managed to work over 2 years (at least half of your PhD) without those samples. How important are those samples to you and your work?