While storing pure hydrogen in salt caverns has been practiced since the 70s in Europe, pure hydrogen storage has not yet been carried out anywhere in depleted fields or aquifers. The Hystories project [1] is delivering technical developments applicable to a vast range of future aquifer or depleted field storage sites and is providing insights into underground hydrogen storage for decision makers in government and industry. It has started in January 2021, is gathering 24 European Companies, Universities or Research Institutes (as Partners or Third Parties), is supported by an advisory board composed of 13 large European companies and will have half of its results delivered by the time of the conference. Some results will be presented in detail during this WHEC. The present paper will complement them by giving an overall view on the technical gaps and improvements, and on the techno-economic insights for hydrogen subsurface storage.