Demand for micron scale polymer particles and capsules has boomed in recent decades, evidenced by the growth in citations of academic papers in the field, alongside consistently over 100 patents granted annually, illustrated in Figure 4.1(a) and (b), respectively. The significant interest stems from the plethora of precise fabrication approaches and growing applications for polymer microparticles and capsules as functional materials.^1–3  Applications include encapsulation of small molecules, colloids and biomolecules and subsequent release following an appropriate stimulus, employed in common laundry and food products, to advanced drug delivery and therapeutic uses.^4–6  For instance, recent developments have demonstrated the encapsulation of fluorescently labelled colloids or quantum dots to impart optical ‘barcodes’ onto particles, paving the way for big data approaches, such as high-throughput multiplexed biomolecular detection.^7,8  Microparticles comprising organic polymers can exploit both their tuneable chemistry and high surface area in catalysis, and chiral and gas separations.^9,10  A number of applications benefit from the ability to form microparticles of non-spherical shapes, and/or patchiness, access a plethora of unique physical,^11–13  optical and sensory properties,^14,15  and enable the predictive self-assembly of such colloidal ‘building blocks’ into highly ordered structures.^16–18