A microelectronic assembly, comprising: a first microelectronic element and a second microelectronic element , each of the microelectronic elements embodying active semiconductor devices adjacent a front surface thereof, each microelectronic element having a rear surface remote from the respective front surface, and each having an electrically conductive pad exposed at the respective front surface; an interposer of a material having a coefficient of thermal expansion less than 10 parts per million/°C, the interposer having oppositely facing first and second surfaces and a second conductive element extending within an opening in the interposer and being exposed at the first and second surfaces, the first surface facing the front surface of the first microelectronic element, and the second surface facing the front surface of the second microelectronic element; characterized in that each of the first and second microelectronic elements (202 and 212) further including a first conductive element (236 and 238) extending within an opening extending from the rear surface of the respective microelectronic element towards the front surface of the respective microelectronic element, wherein at least one of the first conductive elements (236 and 238) extends through the electrically conductive pad of the respective first or second microelectronic element, and the first conductive elements (236 and 238) are electrically coupled with the second conductive element , wherein the second conductive element includes second electrically conductive pads (226 and 228) exposed at the first and second surfaces of the interposer, the pads of the first and second microelectronic elements being first pads, the first pads being juxtaposed with the second pads (226 and 228), and the first conductive elements (236 and 238) contacting juxtaposed surfaces of the first and second pads (204, 214 and 226 and 228). a first microelectronic element and a second microelectronic element , each of the microelectronic elements embodying active semiconductor devices adjacent a front surface thereof, each microelectronic element having a rear surface remote from the respective front surface, and each having an electrically conductive pad exposed at the respective front surface; an interposer of a material having a coefficient of thermal expansion less than 10 parts per million/°C, the interposer having oppositely facing first and second surfaces and a second conductive element extending within an opening in the interposer and being exposed at the first and second surfaces, the first surface facing the front surface of the first microelectronic element, and the second surface facing the front surface of the second microelectronic element; characterized in that each of the first and second microelectronic elements (202 and 212) further including a first conductive element (236 and 238) extending within an opening extending from the rear surface of the respective microelectronic element towards the front surface of the respective microelectronic element, wherein at least one of the first conductive elements (236 and 238) extends through the electrically conductive pad of the respective first or second microelectronic element, and the first conductive elements (236 and 238) are electrically coupled with the second conductive element , wherein the second conductive element includes second electrically conductive pads (226 and 228) exposed at the first and second surfaces of the interposer, the pads of the first and second microelectronic elements being first pads, the first pads being juxtaposed with the second pads (226 and 228), and the first conductive elements (236 and 238) contacting juxtaposed surfaces of the first and second pads (204, 214 and 226 and 228). <EOS>