Abstract: Data-storage devices and methods are disclosed. An exemplary data-storage device includes a medium having at least two dimensions and having a surface. Multiple data-containing loci are arranged on the surface. Each locus has a respective amount of magnetically responsive particles. The respective amounts are different in at least some of the loci. The respective amount at a particular locus corresponds, at least in part, to a respective unit of data contained by the locus. The loci can be substantially two-dimensional or three-dimensional, the latter being configured as respective holes, containing respective amounts of magnetically responsive particles, extending depth-wise into the medium. The loci typically range in size from the micrometer range to the nanometer range. The medium can be any of various configurations such as cards, sheets, films, etc.