A device for mixing small volumes of a first liquid (1, 51) and a second liquid (2, 52), the device comprising a tube (4, 54, 104) having a line cross-sectional area of at most 2 mm 2 or having an inner diameter of at most 1.5 mm, wherein the tube (4, 54, 104) has an open end (43, 93, 143), a main line (5, 55, 105), which is connected to the tube (4, 54, 104) in a liquid-permeable manner on the side opposite the open end (43, 93, 143), at least one body (6, 56, 106), which delimits a line wall of the main line (5, 55, 105) at least in some regions or which delimits the entire main line (5, 55, 105), at least one secondary line (7, 57, 107), which is formed in the at least one body (6, 56, 106), wherein the at least one secondary line (7, 57, 107) extends from at least one secondary opening (8, 58, 108) in the surface of the at least one body (6, 56, 106) up to the main line (5, 55, 105) and opens into the main line (5, 55, 105) via at least one mouth (9, 59, 109) in the at least one body (6, 56, 106), a main connection (10, 60, 110) for introducing a first liquid (1, 51) into the main line (5, 55, 105), at least one feed line (12, 62, 112) for introducing a second liquid (2, 52) into the at least one secondary line (7, 57, 107), wherein the at least one feed line (12, 62, 112) is connected to the at least one secondary opening (8, 58, 108) in a liquid-permeable manner, characterized in that the at least one body (6, 56, 106) is at least one rubber-elastic body (6, 56, 106) and that the at least one secondary line (7, 57, 107) is closed in the at least one rubber-elastic body (6, 56, 106) without the action of a force and is hydraulically openable by a pressure being exerted on a second liquid (2, 52), supplied to the at least one secondary line (7, 57, 107), by an elastic deformation of the at least one rubber-elastic body (6, 56, 106), and wherein the open at least one secondary line (7, 57, 107) closes without a pressure being exerted on the supplied second liquid (2, 52) by the restoring force of the elastically deformed at least one rubber-elastic body (6, 56, 106). a tube (4, 54, 104) having a line cross-sectional area of at most 2 mm 2 or having an inner diameter of at most 1.5 mm, wherein the tube (4, 54, 104) has an open end (43, 93, 143), a main line (5, 55, 105), which is connected to the tube (4, 54, 104) in a liquid-permeable manner on the side opposite the open end (43, 93, 143), at least one body (6, 56, 106), which delimits a line wall of the main line (5, 55, 105) at least in some regions or which delimits the entire main line (5, 55, 105), at least one secondary line (7, 57, 107), which is formed in the at least one body (6, 56, 106), wherein the at least one secondary line (7, 57, 107) extends from at least one secondary opening (8, 58, 108) in the surface of the at least one body (6, 56, 106) up to the main line (5, 55, 105) and opens into the main line (5, 55, 105) via at least one mouth (9, 59, 109) in the at least one body (6, 56, 106), a main connection (10, 60, 110) for introducing a first liquid (1, 51) into the main line (5, 55, 105), at least one feed line (12, 62, 112) for introducing a second liquid (2, 52) into the at least one secondary line (7, 57, 107), wherein the at least one feed line (12, 62, 112) is connected to the at least one secondary opening (8, 58, 108) in a liquid-permeable manner, characterized in that the at least one body (6, 56, 106) is at least one rubber-elastic body (6, 56, 106) and that the at least one secondary line (7, 57, 107) is closed in the at least one rubber-elastic body (6, 56, 106) without the action of a force and is hydraulically openable by a pressure being exerted on a second liquid (2, 52), supplied to the at least one secondary line (7, 57, 107), by an elastic deformation of the at least one rubber-elastic body (6, 56, 106), and wherein the open at least one secondary line (7, 57, 107) closes without a pressure being exerted on the supplied second liquid (2, 52) by the restoring force of the elastically deformed at least one rubber-elastic body (6, 56, 106).