Although the first research on the creative process was based on interviews with the aim of identifying the main stages (macro-process), in the last 50 years researchers have focused more on the analysis of micro-processes, i.e., the mechanisms underlying the generation of ideas. This interest in the micro-processes is partly a result of the tools available to researchers to carry out rigorous studies on the creative process. In this article, we present a useful and relevant analytical tool for macro-processes to assess the creative process in a natural context and when it occurs. Here, the reader will find advice on establishing a research protocol for the creative process by using diaries. Examples of diaries and results are presented. The advantage of this tool is that it enables a direct, rich, and inexpensive assessment of the creative process. Thus, the ecological validity of the diary method is particularly high.