The majority of tokens on Fusion is likely to be aTokens, cross-chain assets brought to Fusion through AnySwap bridging.
So let's take a deeper look on how these work. The concept is similar to LILO described in the Fusion white paper. LILO stands for Lock in, lock out and entails sending tokens (note, the bridger does in many cases not need to do the sending, instead it happens as a bridging transaction, but in practice the tokens are sent) on one chain into a contract controlled by DCRM nodes (meaning no single one of these nodes has direct control, learn more about this sMPC decentralized custody here).
Once securely locked a flexible token contract on the destination chain will initiate a minting contract to mint an equal amount of aTokens and send them to the bridger on the destination chain. The aTokens can be moved freely on the new chain in whatever way the owner wants and can also switch owners without any issues.
If someone wishes to redeem aTokens, the opposite happens. As the owner "redeems" aTokens are sent back into the contract and destroyed and after confirmation an equal amount of locked tokens on the original chain is sent to the redeemer. Generally Redeeming will come at a higher cost than bridging on AnySwap, since AnySwap desires the quantity of aTokens to be increasing effectively increasing TVL (Total Value Locked) which many use as guideline when speculating on the value of ANY.
There can be an infinite amount of various aTokens created through AnySwap bridging coming from various blockchains. A list of currently bridged tokens can be found here. If you desire to initiate bridging of some token to some other chain that's not on the list, you can apply for this here.
There is some future advancements for aTokens planned that differ from the original LILO concept. These are 1. Routing, which means that it'd be possible to more easily switch between the supported networks of an aToken without redeeming it to the original chain. 2. Initiating direct cross-chain transactions without worrying about the intermediary phase of aTokens. All the steps of LILO will still happen in these cross-chain transactions, but much more efficiently and without the cross-chain swapper needing to think about it.
Some of the biggest aTokens are currently aUSDT, aBTC, aETH, aLTC, aFSN and aFTM. These are perhaps the most likely to eventually be seen on many, many chains, while most aTokens might settle for presence on just a few chains that they see value in. But we'll see, it's kind of a question on supply and demand after all. I can see a couple newcomers like aXMR and aDOGE going wide and wild once available for bridging.
Things to keep in mind regarding aTokens:
-All aTokens are of course possible to use for providing liquidity on the AnySwap Exchange but use is not limited to this. They could be used in any DeFi protocol on the destination chain that chooses to have them (and true DeFi protocols are usually open to any token, without special consent).
-aTokens on Fusion are FRC20s and not Fusion assets.
-Highly liquid aTokens pools (on AnySwap and on other DEXes) will have a special role to play in facilitating viable cross-chain transactions, in addition to ANY pools.