Decision-makers are facing the challenge of balancing different factors in the midst of an increasingly complex world. The development of appropriate strategies and policy instruments requires information on system behaviour. Modelling and data-driven decision support tools have become essential for this task, turning vast data into actionable insights. By capturing system dynamics, these tools optimize resource allocation and provide a comprehensive view of interconnected processes, helping navigate complex systems with greater precision. This chapter begins with a general definition of models and their scope of application. It highlights the need for modelling to understand and predict the behaviour of human and natural systems within a developing bioeconomy. An overview of the main types of models at different scales of decision making is provided as well as an introduction to scenario development and its application.