Cataracts have many potential risk factors but the molecular mechanisms underlying their development are unclear. Aggregates of lens epithelial cells (LECs) derived from human pluripotent stem cells (hPSCs) are a potentially powerful in vitro tool to tackle this problem, but existing protocols have a number of shortcomings, including the aggregates’ inability to focus light. Michael O'Connor and colleagues describe an efficient system for the derivation of LECs from hPSCs, and the subsequent creation of light-focusing ‘micro-lenses’ (dev155838). The cell surface marker ROR1 allows for sorting and purification of LECs, which are then cultured as spherical aggregates. Over the course of around three weeks, the aggregates develop the ability to focus light, associated with the expression of crystalline genes and anatomical maturation to mimic lens morphology in vivo. The micro-lenses promise to be clinically relevant, as shown by an analysis of Vx-770, an emerging cystic fibrosis drug that has an as-yet-unclear association with cataract formation. The authors find that culturing with high concentrations of Vx-770 reduces the light-focusing ability of micro-lenses. hPSC-derived micro-lenses therefore provide a powerful in vitro model for research into lens disorders, their risk factors and their molecular underpinnings.