All plastids are ultimately descended from a cyanobacterial ancestor integrated by a eukaryotic cell through primary endosymbiosis. However, most of the diversity of plastid-bearing organisms is the result of endosymbiotic exchange between eukaryotes that have occurred independently and repeatedly in various unrelated lineages. During each of these plastid re-establishments, gene transfer to the host nucleus, formation of protein and metabolite import into the plastid, spatial integration of the new organelle into the host cell and membrane architecture, and rewiring of metabolic pathways around it must take place. Remarkably, highly similar solutions using similar or identical tools and building blocks are often employed in unrelated host-organelle systems. In this chapter, we attempt to summarize and compare various characters across the currently known plastid-type diversity and discuss the trends in their evolution—conservation, reduction, diversification, or convergence—and the possible driving or constraining mechanisms behind them.