The aim of this paper is to engage with the interplay between representational content and design in chemistry and to explore some of its epistemological consequences. Constraints on representational content arising from the aspectual structure of representation can be manipulated by design. Designs are epistemologically important because representational content, hence our knowledge of target systems in chemistry, can change with design. The significance of this claim is that while it has been recognised that the way one conveys information makes a difference to the inferences one can draw from representations in spite of the invariance of informational content, the present paper argues that in chemistry and biochemistry it is often the case that designs have cognitive priority relative to informational content.