Large or small, experienced or new startup, started with Agile and Scrum already or not, the first step everyone takes is setting up Scrum Teams.
Follow the rules and it should just work: deliver software at least 4 times faster and not disturb the rest of the organization. Based on standard Agile and Scrum training materials, a reasonable expectation. But anyone who thinks they can get away with introducing Scrum, getting the benefits, while not disturbing the rest of the organization is in for a big shock.
I will share my experience with an Agile transformation in a 100-person subset of a large software project, in the context of a 27000-person worldwide software development organization going Agile. The good, the bad, and the ugly. What we did about it and what remained to be done.
If you're new at it, so that you won't be shocked. If you're already into it, to understand what that nagging headache is and how to start feeling better.