The instinct you bring from wholesale payments, that a settlement network needs an operator with a rulebook and a membership agreement before anyone is allowed to move value across it, is precisely the assumption public blockchains were designed to delete. A public blockchain is a settlement network with no operator, no membership desk, and no business hours: anyone can run the software, anyone can validate transactions, and the network pays for its own security with a native token rather than member fees. That is not a toy version of a payment system. It is a parallel market structure with its own security budget, its own fee market, and its own definition of settlement, and the largest institutional tokenisation programmes now issue onto it directly.
What a public chain is
Two properties define the category. First, validation is permissionless. The set of machines that order transactions and agree the state of the ledger is open to anyone who meets a protocol rule (burning electricity, or posting a stake of the native token), not anyone who signs a contract. There is no admission committee to petition and no operator to sue, which is exactly the property that makes the permissioned versus permissionless distinction the first fork in any architecture conversation.
Second, the chain has a native token, and the token is not a branding exercise. It is the instrument that pays for the chain's security. Validators are compensated in it, transaction fees are denominated in it, and its market value is, in a loose but real sense, the network's security budget. When a bank hears "ETH" it should think less "speculative asset" and more "the thing that funds the validator set".
Consensus and gas
Bitcoin pioneered PoW (proof-of-work): validators, called miners, race to solve a computational puzzle, and the winner appends the next block and collects newly issued BTC plus fees. Rewriting history would require redoing that computation faster than the honest network, so security is bought with electricity. It is deliberately expensive, deliberately slow, and remarkably durable.
Ethereum ran PoW until the Merge, its switch to PoS (proof-of-stake) completed on 15 September 2022. Under PoS, validators post a stake of ETH as a bond; if they sign conflicting blocks or otherwise misbehave, the protocol destroys part of that stake (slashing). Security is bought with capital at risk rather than energy, which cut Ethereum's energy use by orders of magnitude and, more relevantly for an institutional reader, gave the chain a form of economic finality discussed below.
Every transaction also pays gas, the fee that compensates validators for computation and blockspace. Gas is a floating market, not a tariff card: fees rise when the chain is congested and fall when it is quiet, and users can bid a priority fee to jump the queue. A payment that costs cents on a quiet Sunday can cost dollars during a volatile session. Fee volatility is a genuine operational parameter, and it is the main commercial argument for the L2 (layer-2) rollups described in the chain map.
Finality on a public chain
Here banking intuition will actively mislead. In a designated payment system, finality is a legal fact: a statute says the transfer is irrevocable from a defined moment, insolvency clawback included. On a public chain, finality is a probabilistic or economic fact. A Bitcoin transaction becomes final in the sense that reversing it grows exponentially more expensive with each block piled on top (the six-confirmation convention). An Ethereum transaction becomes final in the sense that reverting it after finalisation, roughly thirteen minutes, would require destroying at least a third of all staked ETH. Neither statement is a statutory guarantee, and no insolvency court is bound by either. The full treatment is in the finality chapter. The one-line version: public chains offer settlement assurance that is very strong in practice and legally undesignated, and a desk should be able to say both halves of that sentence.
The chain map
Five networks cover most of what an operator will actually encounter.
- Bitcoin. The original chain and still the largest asset. Its supply is capped at 21 million coins by protocol rule, its programmability is deliberately limited, and institutionally it trades as a store-of-value asset (a commodity in most regulatory treatments), not an issuance venue.
- Ethereum. The smart-contract anchor of the industry and the default venue for institutional issuance, stewarded at the protocol-research level by the Ethereum Foundation. Most serious tokenised-fund, stablecoin, and tokenised-bond activity touches Ethereum first.
- L2 rollups (Base, Arbitrum, Optimism). Networks that execute transactions cheaply off the main chain, then post compressed proofs back to Ethereum, inheriting its security while cutting fees dramatically. Base is operated by Coinbase, which tells you how comfortable regulated firms have become running chain infrastructure.
- Solana. A monolithic high-throughput design that keeps everything on one fast L1 (layer-1) instead of layering rollups, trading some decentralisation conservatism for speed and low fees. Institutional issuance there is real and growing.
- Tron. Rarely discussed in Western institutional circles and enormously used in practice: it is the workhorse rail for USDT (Tether's US-dollar stablecoin) in Asian and emerging-market corridors, with more than $90 billion of USDT circulating on Tron as of July 2026.
Where institutional issuance lives
The reason a tokenisation desk needs this map is that the flagship institutional products live on these rails, not on bank-built ones. The BlackRock USD Institutional Digital Liquidity Fund (BUIDL), issued by BlackRock through Securitize, launched on Ethereum in March 2024 and had reached roughly $1.7 billion by March 2025, when it added a Solana share class alongside Arbitrum, Optimism, and other networks. The pattern generalises: Ethereum as the anchor venue, L2s and Solana as distribution, permissioned rails (covered in the permissioned chains chapter) reserved for the flows that need a legal perimeter. The next part covers what holding assets on these networks actually means: keys, wallets, and custody.