Recessed ceiling lights seem like the simplest lighting in the world: small, unobtrusive, and they fit anywhere. And yet, it is with these that the most design mistakes are made—from the infamous “airport” effect created by twenty spotlights on the ceiling to shadows on the face in the bathroom. The difference between a professionally lit interior and one lit haphazardly is almost always a matter of placement, not the number of fixtures. In this guide: distances from walls and between tiles, number of tiles per square meter, selecting tiles for bathrooms and kitchens, and step-by-step installation.