Using external representations (ERs) to foster content understanding in biology education has increased as they allow for the visualization of abstract biological phenomena. However, the extent to which students have visualization skills required to learn from ERs effectively remains an open question. The current quantitative quasi-experimental research sought to determine the extent to which an animation could be used to enhance students' visualization skills and reduce learning difficulties related to basic concepts of mitosis. Participants were 67 Grade 10 purposively selected learners from a South African school. An assessment test was used for data collection. Results showed that exposure to an animation, as an additional learning tool, improved students' visualization skills while reducing visualization difficulties related to basic concepts of mitosis. We conclude that ERs may enhance students' visualization skills, reduce learning difficulties and improve content understanding. ERs may also be used in broader student development which includes visual literacy.