Scientific American *How Things Work Today*, 2000 holds data in arrays of [[Capacitors|capacitors]] on a silicon chip - 15 microsecond refresh time Come in SIMM and DIMM form factors - SIMM - Single In-line Memory Module - DIMM - Double In-line Memory Module - each contain chips with array of [[Transistors|transistors]] - connected to capacitor - binary data encoded to capacitor storage