Despite ongoing advancements , biofabrication approaches often depend on monoclonal colonies 219 . These systems may lack the intracellular and intercellular complexity required by specialized cell types and organs, as exemplified by the spider silk gland example. Bacterial consortia partially address this limitation, notably in biomineralization , but solutions remain to be found for material-producing multicellular organs , which are not covered by current engineering approaches . This leaves a research gap at intermediate scales, between top-down and bottom-up biofabrication strategies. A rational approach to biofabrication may bridge this gap, by directing resources exclusively toward a necessary and sufficient organ, without requiring an entire organism. For instance, snake venom gland organoids produce toxins for anti-venom research without the need to develop other organs, such as the brain . This approach could also enable new functionalities and benefits; i.e. removing the risk of accidental bites from traditional snake breeding 225 . To rationalize biofabrication even further, tissues can themselves be edited and improved , such as multicellular engineered living systems (M-CELS) . We propose to define such rational approach as selfmicrofabrication: the process of fabricating structures at microscopic scale through self-organization. Conventional microfabrication in the semiconductor industry already creates desired patterns , but barely uses self-organization 229 . Selfmicrofabrication also builds microstructures guided by DNAencoded patterns, and achieves an unprecedented level of control over complex material self-assembly 230 . This property differs from passive thermodynamic processes 231 , such as phase transitions in metals, with its common use of energy-dependent molecular chaperones or nanoreactors 232 . Thus, selfmicrofabrication occurs at multiple scales: self-organizing both production units (organogenesis) and materials (molecular selfassembly). This article explores these principles, exemplified by organoids producing materials (Fig. ).