Atoms, molecules, enzymes, proteins, DNAs, RNAs, nanoparticles, microparticles, tiles, and bricks are some of the most commonly encountered building blocks in chemistry and architecture. These building blocks can be grouped into subnanometer (atoms), nanometer (molecules, enzymes, proteins, DNAs, RNAs, and nanoparticles), micrometer (microparticles), and millimeter-to-centimeter (tiles and bricks) building blocks based on their sizes. One of the important applications of building blocks is to organize them as monolayers on various substrates. Selfassembly has been the method of choice for the monolayer assembly of nanometer and micrometer building blocks on substrates, whereas direct attachment of building blocks with the hands (referred to as “direct attachment” hereafter) on adhesive-coated substrates is the method for the monolayer assembly of millimeter-to-centimeter building blocks on substrates (floors and walls). Thus, the method for monolayer attachment of building blocks on substrates has to switch from self-assembly to direct attachment at some stage as the size of the building block increases. But what is the upper size limit for self-assembly?What is the lower size limit for direct attachment? At what size regime do both selfassembly and direct attachment work simultaneously for monolayer assembly? In the overlapping region, which method is better in terms of quality of the monolayer? Herein, we report that the upper size limit for selfassembly is 3 mm, the lower size limit for direct attachment is 0.5 mm, and direct attachment is superior to self-assembly in the overlapping region ( 0.5–3 mm) with respect to rate, degree of close packing, uniform orientation of the assembled microcrystals, substrate area, and ecological considerations. We used zeolite microcrystals as model system because they can be produced in fairly uniform sizes and shapes, and their monolayers can be applied as precursors for molecular sieve membranes, low-dielectric materials, supramolecular energy-transfer systems, nonlinear optical films, anisotropic photoluminescent films, and other advanced materials. Silicalite-1 and ETS-10 (see the Supporting Information) crystals were used in this study. In the case of silicalite-1, crystals with four different sizes were employed. The average sizes and volumes [a:b: c (volume)] were: 0.3 : 0.1 : 0.6 (0.02), 1.3 : 0.5 : 1.7 (1.11), 2.5 : 1.2 : 4.1 (12.3), and 4.6 : 1.5 : 11 mm (75.9 mm). In the case of ETS-10, only crystals with an average size of 12 : 12: 7 mm (1008 mm) were used. The volume ratio for these crystals was 1:56:615:3795:50400. Glass plates with two different sizes, 18 : 18 and 150: 150 mm, were used as the substrates. Among various tested types of bonding between microcrystals and substrates, we found that ionic bonding and hydrogen bonding (Figure 1) were most effective for the monolayer assembly of microcrystals by direct attachment. The ionic bonding was induced between trimethylpropylam