A system for counting cells (100; 200) or biomolecules comprising: a covered sample chamber (101; 201) having a known height and configured to hold a suspension of biomolecules or cells in a liquid sample; at least one fluorescent light source (102; 202) connected to at least one fluorescent light beam narrowing device (103; 203); a bright-field light source (104; 204) connected to a bright-field light beam narrowing device (105; 205), wherein the bright-field light beam narrowing device (105; 205) is positioned between the sample chamber (101; 201) and the bright-field light source (104; 204), and wherein the bright-field light source (104; 204) is configured to emit light onto the liquid sample in the sample chamber (101; 201) positioned in-line above the bright-field light source (104; 204); a microscope objective (106; 206); a detection device (107; 207); a fluorescent filter assembly (110; 210) to allow excitation light from the fluorescent light source (102; 202) to illuminate the sample but not to illuminate the detection device (107; 207), and allow emission light from the sample to be imaged by the detection device (107; 207), wherein the fluorescent filter assembly (110; 210) is positioned in-line with the bright-field light source (104; 204), the bright-field beam narrowing device (105; 205), the sample chamber (101; 201), the microscopic objective (106; 206) and the detection device (107; 207); and a movable light shutter (108; 208), positioned between the sample chamber (101; 201) and the bright-field light source (104; 204), to block bright-field light during fluorescent detection, wherein the fluorescent light source (102; 202) and the detection device (107; 207) are both located on the opposite side of the sample chamber (101; 201) with regard to the bright-field light source (104; 204); and the volume of the covered sample chamber (101; 201) under interrogation by the fluorescent and bright-field lights is known for each image taken. a covered sample chamber (101; 201) having a known height and configured to hold a suspension of biomolecules or cells in a liquid sample; at least one fluorescent light source (102; 202) connected to at least one fluorescent light beam narrowing device (103; 203); a bright-field light source (104; 204) connected to a bright-field light beam narrowing device (105; 205), wherein the bright-field light beam narrowing device (105; 205) is positioned between the sample chamber (101; 201) and the bright-field light source (104; 204), and wherein the bright-field light source (104; 204) is configured to emit light onto the liquid sample in the sample chamber (101; 201) positioned in-line above the bright-field light source (104; 204); a microscope objective (106; 206); a detection device (107; 207); a fluorescent filter assembly (110; 210) to allow excitation light from the fluorescent light source (102; 202) to illuminate the sample but not to illuminate the detection device (107; 207), and allow emission light from the sample to be imaged by the detection device (107; 207), wherein the fluorescent filter assembly (110; 210) is positioned in-line with the bright-field light source (104; 204), the bright-field beam narrowing device (105; 205), the sample chamber (101; 201), the microscopic objective (106; 206) and the detection device (107; 207); and a movable light shutter (108; 208), positioned between the sample chamber (101; 201) and the bright-field light source (104; 204), to block bright-field light during fluorescent detection, the fluorescent light source (102; 202) and the detection device (107; 207) are both located on the opposite side of the sample chamber (101; 201) with regard to the bright-field light source (104; 204); and the volume of the covered sample chamber (101; 201) under interrogation by the fluorescent and bright-field lights is known for each image taken.