I am responsible for running a health and demographic surveillance system (HDSS) in Guinea-Bissau. This has trained my research skills and made me develop a critical view on why interventions are recommended and implemented the way they are. To ensure optimal data quality, I have frequently been present when the data is collected; this has not only strengthened the HDSS, but also my skills: Making the observations and noticing when reality contradicts assumptions, allows me to ask the right questions, and formulate hypotheses, which I, with access to data and the skills to analyse them, can test.