Absolutely! One of the aspects of my thesis project was to develop an in vitro blood-brain barrier; primary cortical neuronal cells would be attached to the bottom of a well while endothelial cells and astrocytes would be suspended on either side of a transwell above the neurons. I thought the first task, culturing the neurons, would be very quick, simple, and, therefore, extraneous while executing the transwell would require time and development of skill. However, the neuronal culture was much more difficult than I anticipated and they became a critical path. It turned out that neurons are very fickle because they can get easily stressed by their surroundings and how they are handled and die. Cortical neuronal cells must be “wined and dined” needing proper time and handling skill for proper culture. From this development and under time constraint I turned my critical path into the focus of my project abandoning the transwell idea and instead studying concentrations of cytokines/HIV proteins on neuronal cell death, trying to pin-point a specific concentration to significant cell death. My seemingly insignificant cell culture turned into a critical path that made me reassess my project and, for time constraint reasons, made me change it.