During their studies of the Borg in the 2350s, Magnus and Erin Hansen used subdermal probes to keep track of specific Borg drones. (VOY: "Dark Frontier") In 2373, The Doctor injected Kathryn Janeway with a subdermal bioprobe so that he could monitor her biochemistry as she underwent a Nechisti Order purification ritual in an effort to save Kes, who had been injured by a Nechisti shrine. The Nechani bio-scanners detected the bioprobe, but they had no objections to Janeway using the device. (VOY: "Sacred Ground")