Two single mesophyll-protoplasts of Nicotiana tabacum cv. xanthi were selected into a 100 nl microdroplet of 0.4 M mannitol. Two cylindrical platinum electrodes were inserted into the microdroplet to align the two single cells via dielectrophoresis in an AC-field (1 MHz, about 120 V X cm-1). A single square DC-pulse of about 1.5 KV X cm-1 was applied to induce protoplast fusion.