—from the Lab Manager's bench
After you reach certain benchmarks in the lab, your research supervisor will transition from the role of supervisor to that of a research mentor.
Accompanying this change in roles will be the growing responsibility to do tasks formerly completed by your research supervisor. This will be unsettling at first--especially when you quickly realize that your success is now in your hands. Long ago, one of my undergrads described this path to self-reliance as "Growing Pains" and it immediately became part of our lab’s lingo.