Lerna is an amazing open source tool for managing JavaScript projects with multiple packages. It allows you to easily maintain multiple packages from a single source, and simplifies the process of publishing updates and managing dependencies. With Lerna, you can control the versioning of all your packages from one place, use a single command to publish updates, and easily manage dependencies across packages. Lerna makes it easy to create and manage a monorepo – a central repository that contains multiple packages – with just a few commands, and helps developers to efficiently manage JavaScript projects of any size and complexity.