Synthetic Biology is increasingly used to implement novel applications in which designer organisms perform complex tasks not easily amenable to traditional engineering methods, such as cancer detection, fuel generation, drug production, and recently even the re-creation of extinct species. From a more fundamental perspective, synthetic biology can also be used to probe the limits and capabilities of cells. A special issue of the RSC Journal Integrative Biology, guest edited by John McCarthy, Jordi Garcia-Ojalvo and Ahmad Khalil, has just been published that features emerging research using synthetic biology to achieve new biological insights.