DIYbio (Do It Yourself Biology) aims to 'open source', tinker and experiment with biology outside of professional settings. In this paper, we present the origins, practices, and challenges of DIYbio initiatives around the world. Our findings depict DIYbio as operating across intersections ('seams') between a range of stakeholders, materials and concerns. To map out the role of Human Computer Interaction (HCI) across these seams, we present design exercises (functional prototypes) that explore three areas for future work: internal collaboration tools within the DIYbio and professional community; mechanisms for external communication with stakeholders from the general public; and bio-electronic assemblies of organic and digital materials. In doing so, we hope to critically re-envision the role of HCI at the emerging intersection of biology, computation and DIY.