There exist isolated star complexes , located sometimes far away from the center of a galaxy or from the spiral arms. These complexes often have spheroidal or arc-like shapes. The best examples are in the LMC, NGC 6946 and NGC 5236. This shape strongly suggests triggering by some energetic events. The striking feature of these complexes is their sharp and circular outer edge. This suggests they are partiall spheres and could be formed from the gaseous supershells. The nature of the events triggered the formation of supershells and more so of these peculiar complexes is the controversial issue.