 Engineering is often promoted through the idea of rational design. Some synthetic biologists have adopted a similar vision of synthetic organisms as structures that can be assembled via replaceable and standardized components, akin to Lego-bricks (front cover of Science, 2 September 2011 [333(6047)]). Yet, philosophers have argued that the actual research practices in synthetic and systems biology paint a different picture (Knuuttila &amp; Loettgers 2013a, 2014).