Most common network visualizations rely on graph drawing. While without doubt useful, graphs suffer from limitations like cluttering and important patterns may not be realized especially when networks change over time. We propose a novel approach for the visualization of user interactions in social networks: a pixel-oriented visualization of a graphical network matrix where activity timelines are folded to inner glyphs within each matrix cell. Users are ordered by similarity which allows to uncover interesting patterns. The visualization is exemplified using social networks based on corporate wikis.