Intertidal biofilms are a diverse mixture of bacteria, algae as well as sporelings of macroalgae embedded in a polysaccharid matrix. As the primary colonisers of newly formed surfaces, biofilms undergo a succession of different microbe assemblage until the mature state is reached. A biofilm can act as primary producers and as such recycle nutrients in a habitat. It will influence macrobiota by providing a food source or sending out cues to settlers. Biofilms themselves will be controlled by these settlers. This interaction between bottom-up and top-down plays a crucial part for the functioning of the rocky shore ecosystems. However, the diversity of biolfilms as well as it nature to react quickly to environmental changes makes identification and quantification of the individual compounds a difficult task. Subsequently, the understanding of biofilms in general and intertidal, rocky shore microbe assemblages has always tied to techniques and methods available at the time of study. This chapter focusses on the techniques that have greatly contributed to increasing knowledge of biofilms and discusses their findings. Nonetheless, newly developed methods promise to further this knowledge of the ecological role of biofilms on rocky coastlines.