= Solution
The map shows \b[<Coulomb blockade> with discrete single-electron charging]: low-current diamonds separate charge-stable regions from finite-bias transport windows. A small conducting island or <quantum dot> must be tunnel-coupled to source and drain, with a gate shifting its <electrochemical potential>. Charging prevents sequential transport until an island addition/removal energy enters the <bias voltage> window.
The tunnel resistances should substantially exceed the <resistance quantum> $h/e^2\simeq25.8\ \mathrm{k\Omega}$, preventing charge fluctuations from washing out integer island occupancy, while still permitting a measurable current. <Temperature> and tunnel broadening must be small compared with the addition-energy scale. Here the smaller diamonds imply $e^2/C_\Sigma\simeq2.5\ \mathrm{meV}$, so $k_BT\ll2.5\ \mathrm{meV}$, or $T\ll29\ \mathrm K$; resolving the inferred 1 meV orbital structure requires the stricter scale $T\ll12\ \mathrm K$. Stray <capacitance> and unintended multiple islands can complicate this simple interpretation.
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