For that, you use `app.add_middleware()` (as in the example for CORS).

```Python
from fastapi import FastAPI
from unicorn import UnicornMiddleware

app = FastAPI()

app.add_middleware(UnicornMiddleware, some_config="rainbow")
```

On the request path, the *outermost* middleware runs first.

On the response path, it runs last.

For example:

```Python
app.add_middleware(MiddlewareA)
app.add_middleware(MiddlewareB)
```