Method for manufacturing metallic pieces including at least two self-assembled superimposed levels obtained by photolithography and electroforming, this method comprising the following steps: - preparing a first mould including a cavity with at least one stage, said first mould defining a first level is prepared according to the following steps: - depositing and irradiating through a first photomask, a first photoresist layer applied on a substrate, - polymerizing the first photoresist layer, - eliminating the non-polymerized photoresist layer, the remaining photoresist part constituting the first mould formed by the photoresist and including at least one cavity. - depositing a first metallic layer by electroforming in the cavity of the first mould, - removing the polymerized photoresist from the first mould, - depositing a second photoresist layer applied on the substrate, irradiating and polymerizing by means of a second photomask, by masking all or part of the first metallic layer except at least one side wall of the first metallic layer, said second photoresist layer, having a thickness equal or greater than the thickness of the first metallic layer, - eliminating the non-polymerized photoresist layer, in order to leave at least one traversing space free of photoresist adjacent to the side wall of the first metallic layer, the method is characterized in that it comprises steps of: - applying a third photoresist layer and irradiating it through a third photomask, having a pattern configured in order to mask an area extending partially or entirely on the first metallic layer, an external area close to said first metallic layer and the space adjacent to the side wall of the first metallic layer, - polymerizing the third photoresist layer and eliminating the non-polymerized photoresist layer, the remaining photoresist part forming a cavity of a second mould, the space adjacent to the side wall of the first metallic layer being free of photoresist. - depositing a second metallic layer by electroforming in the cavity and the space by creating an intimate connection between the second metallic layer and at least one side wall of the first metallic layer and resulting in a self-assembling between the two levels of the piece, - machining, by a mechanical process, the second metallic layer to a predefined thickness, - removing the polymerized photoresist of the mould of the second level as well as the substrate, - obtaining a metallic piece including two superimposed levels interlocking each other, the orthogonal projection of one level extending partially on the orthogonal projection of the other level, the contour and the relative positioning of each level being defined by photolithography. - preparing a first mould including a cavity with at least one stage, said first mould defining a first level is prepared according to the following steps: - depositing and irradiating through a first photomask, a first photoresist layer applied on a substrate, - polymerizing the first photoresist layer, - eliminating the non-polymerized photoresist layer, the remaining photoresist part constituting the first mould formed by the photoresist and including at least one cavity. - depositing a first metallic layer by electroforming in the cavity of the first mould, - removing the polymerized photoresist from the first mould, - depositing a second photoresist layer applied on the substrate, irradiating and polymerizing by means of a second photomask, by masking all or part of the first metallic layer except at least one side wall of the first metallic layer, said second photoresist layer, having a thickness equal or greater than the thickness of the first metallic layer, - eliminating the non-polymerized photoresist layer, in order to leave at least one traversing space free of photoresist adjacent to the side wall of the first metallic layer, - applying a third photoresist layer and irradiating it through a third photomask, having a pattern configured in order to mask an area extending partially or entirely on the first metallic layer, an external area close to said first metallic layer and the space adjacent to the side wall of the first metallic layer, - polymerizing the third photoresist layer and eliminating the non-polymerized photoresist layer, the remaining photoresist part forming a cavity of a second mould, the space adjacent to the side wall of the first metallic layer being free of photoresist. - depositing a second metallic layer by electroforming in the cavity and the space by creating an intimate connection between the second metallic layer and at least one side wall of the first metallic layer and resulting in a self-assembling between the two levels of the piece, - machining, by a mechanical process, the second metallic layer to a predefined thickness, - removing the polymerized photoresist of the mould of the second level as well as the substrate, - obtaining a metallic piece including two superimposed levels interlocking each other, the orthogonal projection of one level extending partially on the orthogonal projection of the other level, the contour and the relative positioning of each level being defined by photolithography.