A method of 3D circuit conception comprising: providing, to a circuit conception tool, circuit design files representing a 3D circuit design including one or more first circuit elements attributed to a first tier of the 3D circuit and one or more second circuit elements attributed to a second tier of the 3D circuit; modifying, by the circuit conception tool, a property of the one or more first and/or second circuit elements to permit any of the second circuit elements to superpose, or be superposed by, any of the first circuit elements; and performing, by the circuit conception tool, placement and routing of the 3D circuit design based on a 2D circuit representation, interconnection nodes of the one or more second circuit elements being defined in one or more interconnection levels of the 2D circuit representation.