In a method for picking up cell material from a culture dish a picking tool is displaced towards the cell material. Contact between the tool and the cell material is determined by carrying out capacitive measurements. After contact the tool is removed from the cell material. In an assembly for performing said method a support made of electrically conducting material supports the dish. A measurement device determines the start electrical capacity of the system composed of picking tool and support in a starting position of the tool, and determines the electrical capacity of the system when lowering the tool towards the dish. The measurement device provides signals representing the electrical capacity to a controller, which comprises a comparator for performing a comparison of the electrical capacity during lowering of the tool with the start electrical capacity. The controller controls the positioning of the tool at least based on this comparison.