The present invention discloses systems and methods for a smart card including: a first card having a device; and a second card having an aperture that is configured to allow a device to be inserted into an aperture when the second card is properly aligned with the first card, thereby allowing a device to protrude into an aperture. Optionally, the first card includes an aperture, and the second card includes a device, so that an aperture of the first card accommodates a device of the second card when the first card is properly aligned with the second card. Optionally, the apertures and the devices are configured to allow a stack of a plurality of the first and second cards to be densely packed Optionally, a card includes a magnetic stripe, an electronic circuit, and/or an embedded electrically-conductive wire for operationally connecting a device to a connector.