Putting complex psychological processes in the centre of analysis opens a field of methodological and disciplinary controversies. One of the first methodical AND methodological controversies to address the question of which processes and how complex mental processes can be researched was ‘introspection’. Since ‘introspection’ became a method of the past in the meantime, I argue that it is necessary to address it in today’s psychological method debates: (1) at the time where research paradigms (qualitative, quantitative and mixed-methods) were not yet established programmes, methodological ‘burning questions’ could be more openly discussed and debated since there were no ‘standard ways’ yet that would conceal them. (2) ‘Introspection’ is still a central concept of psychological research, only hidden behind more accepted labels (self-report questionnaires, interviewing, etc.). With this presentation, I will present results of my analysis of historically controversial methods of ‘introspection’ (mainly by W. Wundt and K. Bühler), and ask for their applicability and value for contemporary psychological research. By first situating ‘introspection’ in the context of the early discipline formation around 1879 and re-reading and re-assessing ‘old’ versions of using ‘introspection’ as a method, and second reviewing contemporary uses of ‘introspection’ (predominantly Dialogic Introspection, Descriptive Experience Sampling Method), I will address the fundamental question how contemporary psychology can make use of introspective methodologies. My analysis will show that under specific conditions, ‘introspection’ offers systematic empirical access to complex psychological processes. I will present different ‘strata’ of introspective reality and will deduct acceptance criteria of introspective research for today’s psychological research.