The high expectations placed on forests in Europe require an integrative approach to forest management. Heterogeneous mixed-species stands are of special interest as they fulfil many ecosystem services better than monocultures, and consequently homogenous forest stands are now often transformed into more heterogeneous stands. This chapter contrasts even-aged monoculture forests and selection forests, describing the transition from monocultures to more complex forest stands. The chapter presents practical examples of transformation and models for scenario analysis, as well as explaining the principles of selection forest management. Finally, the chapter looks ahead to future research trends in this area.