Engineering began as an outgrowth of the craftwork of metallurgical artisans. In a constant quest to improve their handiwork, those craftsmen exhaustively and empirically explored the properties—alone and in combination—of natural materials. The knowledge accumulated from this exploration and experimentation with natural building blocks eventually led to today’s modern technologies. We can now readily build things like super-lightweight cars and electrical circuits containing billions of transistors that encode highly sophisticated functions, using reliable design and manufacturing frameworks—a vast leap from artisanal craft.Today, there is a parallel progression unfolding in the field of synthetic biology, which encompasses the engineering of biological systems from genetically encoded molecular components.1-7 The first decade or so of synthetic biology can be viewed as an artisanal exploration of subcellular material. Much as in the early days of other engineering disciplines, the field’s focus has been on identifying the building blocks that may be useful for constructing synthetic biological circuits—and determining the practical rules for connecting them into functional systems. This artisanal tinkering with cells is necessary for arriving at a rigorous understanding of subcellular construction material and for determining the extent to which it can be manipulated.