Inquiry-Based Science Education (IBSE) is considered to be an innovative educational method which has a strong motivational effect on students and teachers. The presented research tries to answer questions aimed at: the characteristics of experiments at each of the IBSE levels, principles for applying IBSE experiments, and teacher training methods suitable for IBSE experimentation. A mixed research method combining a theoretical comparative analysis and design-based research, was used. The taxonomy of IBSE experiments and the principles for their implementation into teaching/learning science must be added to pre-service and in-service science teacher training. This task is performed by the European project PROFILES.