At first glance, bacteria that belong to the two genera Streptomyces and Mycobacterium of the phylum Actinobacteria show no sign of similarity. Whereas Streptomyces species are generally classified as spore-forming, filamentous bacteria, species of the Mycobacterium genus have been considered non-sporulating, rod-like shaped. However, recent studies in genetics and cell biology of Streptomyces and Mycobacterium have revealed striking analogies in the developmental and morphological hallmarks of their life cycles. Understanding the mechanisms underlying these similarities, as well as variations in morphogenesis and development of these two groups of bacteria may not only provide important insights in the evolution of cell shapes in Actinobacteria, but also lead to medical interventions that impact human health.