Arthrospira platensis (AP) is a cyanobacterium with a high economic value and is nowadays one of the most important industrially cultivated microalgae. Knowledge of its growth is essential for the understanding of its physiology and yield. The growth of AP biomass occurs through two mechanisms: (1) propagation by fragmentation of trichomes, and (2) the trichomes are extended by binary fission until they reach their mature status. These phases are visualized by live cell light and laser scanning microscopy, demonstrating the different phases of AP growth.