Methods for forming openings having predetermined shapes in a substrate and apparatuses with these openings. The methods may be used to form assemblies which include the substrate with its openings and elements which are disposed in the openings. In one example of a method, each of the elements include an electrical component and are assembled into one of the openings by a fluidic self assembly process. In an particular example of a method to create such an opening, the substrate is etched through a first patterned mask and is later etched through a second patterned mask. Typically, the second patterned mask is aligned relative to the opening created by etching through the first patterned mask and has an area of exposure which is smaller than an area of exposure through the first patterned mask. In another example of a method, a photosensitive material is exposed through a patterned mask to oblique sources of light such that some of the light impinges into a first portion of the photosensitive material which is under the patterned mask, and the patterned mask and a second portion of the photosensitive material, which is under the patterned mask, is removed. In another example of a method, an opening in a first layer, which comprises silicon dioxide, is formed by depositing a second layer over the first layer and depositing a tungsten layer over the second layer. The tungsten and second layers are patterned to expose a portion of the first layer, and this portion is etched. Various apparatuses which may be made using these methods are also described.