The cell is a key concept, and accurate knowledge of it is essential for understanding many phenomena and biological processes, as well as the overall functioning of living beings. However, learning about this concept is not simple. Regarding this concept, we examined the views concerning problems that could be encountered by Master's students training to become future teachers of natural science, compared to the difficulties suffered by a group of students in their last two years of high school. The results show the students' learning about the cell appeared to be negatively influenced by the methodology used in classroom, being this type of difficulties the most reported by the high-school students, followed by difficulties with matters associated with the functional role of the cell. However, the methodology limitations have been the least considered by future teachers. By contrast, they consider the structural aspects of the cell as more likely to be problematic for students, followed by the functional ones. Problems concerning sizes and scales arose similarly in both cases, implying a widespread problem.