This lesson introduces the `?.` operator which is known as [optional chaining](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining). We're going to look at how we can use `?.` to safely descend into an object with properties which potentially hold the values `null` or `undefined`. We're also going to learn how to access properties with an expression using the `?.[]` bracket notation and how to call functions which may not exist using the `?.()` syntax.