the length scales of structure
If structural hierarchy is the idea that structure exists at many nested levels, the length scales of structure are the actual rulers, how big, in meters, each level is. It answers the question, how far do I have to zoom to see this feature? Some features are a fraction of a nanometer (atoms); others are millimeters (a weld seam). Knowing the scale tells you both what tool can see it and what property it might control.
A rough ruler goes like this: an atom is about 0.1 to 0.3 nanometers across (1 to 3 angstrom; 1 angstrom = 10^-10 meter). The repeating unit cell of a crystal is typically 0.3 to 1 nm. Nanostructure spans roughly 1 to 100 nm. Microstructure, meaning grains and phases, runs from about 1 micrometer (1000 nm) to hundreds of micrometers. Macrostructure is anything from about a millimeter up to the whole part. Across this range the length changes by a factor of ten million or more.
Each scale needs its own instrument: X-ray diffraction and electron microscopes reach the atomic scale; optical microscopes see microstructure; the eye and simple magnifiers handle macrostructure. And each scale can own a property, which is why materials people always ask, at what scale? Caveat: the numbers above are conventions with fuzzy, overlapping edges, there is no sharp line where nano becomes micro; the scale ladder is a guide for thinking and choosing tools, not an exact law.
Picture a table lining up scale, feature, and tool: angstrom-sized atoms (X-ray diffraction), nanometer precipitates (transmission electron microscope), micrometer grains (optical microscope), and a millimeter weld bead (the naked eye).
Every length scale has its own features and its own instrument.
A bigger feature is not more structure than a small one. All scales coexist in the same sample at the same time; you simply choose which one to look at by choosing your magnification.