place of service - Goods and Services Tax - GST

sir, Client having stemcell banking business in multiple states , where the collection and processing of the stemcell will be done in the concerned state. After Processing , for storage purpose , the stem cell will stored in the lab loacted at headoffice ( in one state) of the client. can you please advise me the place of service for levy of gst for the transactions in all the states . Whether i need to levy and pay gst in each state for the transactions relating to each state or i have to levy and pay for all the states in head office only? pls advise.