Interest affects learning; it also affects students' attitude towards science and career choices. It is therefore urgent to increase students' interest and improve their attitude towards science to face the complex challenges of the future. This study transformed cutting-edge induced pluripotent stem cells (iPSC) research into an informal science course to explore the effect of students' situational interest (SI), concept understanding and attitude towards science. A total of 52 tenth-grade students of upper secondary school participated in an informal science course including a one-day workshop and exploration in a science museum, and one-day of lab work in a university laboratory. The questionnaire data were analysed by pre- and post-t test to explore the learning outcomes, and the learning experience reports were content analysed to explore the influencing factors. Results showed that 1) students' SI was significantly enhanced, with the trigger and affective components of SI scoring, but not the value component; 2) Students' iPSC concept understanding was significantly enhanced; 3) The course enhanced students' SI, iPSC concept understanding and attitude towards science via different influencing factors; 4) The value factors may influence students' positive attitude towards science and engagement in science. We also present some suggestions for informal science course design and teaching practice.