Complex interventions consist of multiple components, which interact to create intervention effects. Thus, special attention is required concerning the development, the pilot testing, the evaluation and the scientific reporting. Inadequate recognition of the complexity of these interventions by clinicians and researchers may unintentionally prevent implementation of the results of complex interventions. We present a framework, which highlights aspects of the development, the modelling and the analysis of complex interventions, so that clinicians and researchers can untangle "the black box" of these clinical trials.