Animation has great potential for improving the way people learn. A number of studies in different scientific disciplines have shown that instruction involving computer animations can facilitate the understanding of processes at the molecular level. However, using animation alone does not ensure learning. Students sometimes miss essential features when they watch only animations, mainly due to the cognitive load involved. Moreover, students seem to attribute a great deal of authority to the computer and may develop misconceptions by taking animations of abstract concepts too literally. In this study, we attempted to explore teachers' perceptions concerning the use of animations in the classroom while studying biotechnological methods, as well as the teachers' contribution to the enactment of animations in class. Thirty high-school biotechnology teachers participated in a professional development workshop, aimed at investigating how teachers plan for and support learning with animation while studying biotechnological methods in class. From that sample, two teachers agreed to participate in two case studies aimed at characterizing teachers' contribution to the enactment of animations in class while studying biotechnological methods. Our findings reveal marked teacher contribution in the following three aspects: establishing the "hands-on" point of view, helping students deal with the cognitive load that accompanies the use of animation, and implementing constructivist aspects of knowledge construction while studying using animations.