The invention relates to a device (100; 200; 300; 400) for analyzing biological substances in a test solution, comprising a test substrate (101; 203; 303; 401) which is transparent at least in part, having a test region (107a, 108a, 109a, 110a; 211; 411) for receiving the test solution, a plurality of electrodes (111, 106; 201, 202; 301, 302; 402, 403) which are arranged on the test substrate (101; 203; 303; 401) and extend into the test region (107a, 108a, 109a, 110a; 211; 411), wherein in each case, at least one portion of the electrodes (111, 106; 201, 202; 301, 302; 402, 403) is made of a transparent material.