> For the complete documentation index, see [llms.txt](https://stableunit.gitbook.io/documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://stableunit.gitbook.io/documentation/introduction/how-does-it-work.md). # How Does It Work #### How StableUnit Works — and Why USD Pro Earns Yield When a user wants liquidity, they **deposit collateral** (e.g., ETH, USDC, or an LP token) into a StableUnit vault to **borrow USD Pro**. At that moment StableUnit offers a **“Boost collateral”** option:\ • If the user accepts, the protocol instantly routes the collateral into a high-grade, on-chain strategy (staking ETH, restaking, or farming an LP) so the collateral itself starts **earning extra yield**.\ • If the user declines, the collateral simply stays idle in the vault. Either way, the user walks away with liquid USD Pro, but an upgraded vault enjoys a **discounted Borrow rate** because the protocol keeps a slice of the boosted yield. That is the first revenue stream of the StableUnit protocol: **Yield Spread** – the portion of strategy yield captured when users choose the Boosted path. The second one is **Stability Fees** – interest paid by all borrowers on their outstanding USD Pro debt. And the third is **Liquidation Surplus** – when a position is liquidated, any collateral left after repaying debt and fees is swept into protocol revenue. All revenue accumulates in real time and is **rebated to USD Pro holders** every block: the token’s supply (or per-token index) increases continuously, so simply *holding* USD Pro causes the balance in a user’s wallet to rise.