Steem run on a blockchain, albeit one of the fastest ones out there at the moment. [Dan Larimer has developed a blockchain called Graphene](https://hackernoon.com/dan-larimer-visionary-programmer-of-bitshares-steem-and-eos-7e6d94b241d7) the underlies Steem, Steemit, and BitShares. Although Graphene is still not as powerful as Hashgraph, it blows away most other blockchains on the market in terms of performance.

Dan is now working on EOS which should allow even greater underlying blockchain performance as well as a whole lot of other framework capabilities that then don't need to be rebuilt each time someone creates a new blockchain. It wouldn't surprise me for a minute if at some point Steem, Steemit, and BitShares are migrated on top of EOS when it is ready. This would be a very logical future decision.

Since Hashgraph is only a consensus mechanism technology and does not cover all the other bells and whistles built into Steemit or EOS, Hashgraph could easily be used to swap out the underlying Graphene blockchain in Steem or whatever the blockchain in EOS is. This however is assuming that the design of Steemit and EOS is modular enough to allow this. Think of Hashgraph as just the shared ledger / database and all the other features as part of an application sitting on top of it. That's probably the easiest way to approach it.

I hope this answers your question, just let me know if doesn't.