Developing methods to rear phytophagous insects is crucial to reveal the true complexity of interactions between insects and their host plants. Here we focus on leaf-mining insects, an ecological guild across four different orders (Lepidoptera, Diptera, Coleoptera, and Hymenoptera) whose larvae feed inside the leaves of their host plants, producing cavities in the leaf tissue that are known as leaf mines. Besides leaf lamina, some leaf-mining species can also mine leaf petioles and veins, and a few species make cavities in soft shoots, stems, or mine the surface of young fruits and seeds. Most leaf miners are host plant-specific and produce characteristic leaf mines that are remarkably variable among species. Some species are considered important crop, orchard, and forest pests. Despite their fascinating life history, global diversity, and ecological and economic importance, little is known about the biology of most species, in particular in the tropics. Here, we describe methods to collect, rear, and preserve samples of leaf miners with an emphasis on the smallest of Lepidoptera