The current vs. voltage and electrical breakdown behavior for devices with micron and sub-micron gaps between conductors is studied. The limitations of the well-known but often-misinterpreted Paschen curve are discussed. The little-known modified Paschen curve, that includes field emission effects so important in understanding breakdown behavior for devices with sub-micron gaps, is described. Current vs. voltage measurements across metal-air-metal, metal-insulator-metal and metal-insulator-air-insulator-metal gaps with gaps ranging from 4 nm to 4 μm are reported. The breakdown voltage for an air gap of 0.9 μm was found to be 150 V, far below the Paschen curve minimum breakdown limit, and field emission behavior was confirmed via the Fowler-Nordheim plot. Metal-insulator-metal gaps with a diamond-like carbon thin-film with a thickness of 4 nm had a breakdown voltage of only 1V. SEM and AFM analysis show that the breakdown damage is crater-like and through the carbon layer. Other characterization of the damage caused by breakdown is presented. Tribocharging, electrostatic induction, and other ESD-related phenomena, are discussed for several devices with sub-micron gaps. It is concluded that devices with sub-micron gaps can face a serious challenge due to electrical breakdown during manufacturing, handling and operation. These devices include photolithographic reticles, magnetic recording heads, MEMS and field emission displays.