A method for quantifying the cultivability of individual microbial cells using culture independent parameters, comprising the following steps of (i) contacting a sample comprising microbial cells with a nucleic acid binding fluorescent dye to stain cellular nucleic acids in said microbial cells; (ii) subjecting the labelled cells to a fluorescence microscopy imaging method and determining, based on the nucleic acid staining, for a plurality of single cells at least a first parameter reflecting the nucleic acid content of said cell and a second parameter reflecting the extent of stretching of said cell; wherein determining said at least first and second parameter comprises analysis of a crude fluorescence microscopic image using a thresholding algorithm to obtain a binary filter image, and making an overlay of the binary and crude filter image to determine the average grey value, standard deviation and surface area of individual cells, and wherein the nucleic acid content is calculated on the basis of the following equation: nucleic acid content = log standard deviation per microbial cell log average grey value per microbial cell (iii) classifying based on said at least first and second parameter said cell into one of the following categories: Viable cultivable cells with a nucleic acid content value between ≥0.1 and 1.0 and extent of stretching of the cell value between ≥1.0 and 10 μm 2, Viable non-cultivable cells with a nucleic acid content value of ≥-0.2 and extent of stretching of the cell value of ≥0.5 μm 2 minus Viable cultivable cells, Most likely dead cells with a nucleic acid content of <1.0 and extent of stretching of the cell value of <0.5 μm 2; and (iv) calculating the ratio of the amount of viable cultivable cells, viable non-cultivable cells and most likely dead cells in a microbial sample. (i) contacting a sample comprising microbial cells with a nucleic acid binding fluorescent dye to stain cellular nucleic acids in said microbial cells; (ii) subjecting the labelled cells to a fluorescence microscopy imaging method and determining, based on the nucleic acid staining, for a plurality of single cells at least a first parameter reflecting the nucleic acid content of said cell and a second parameter reflecting the extent of stretching of said cell; wherein determining said at least first and second parameter comprises analysis of a crude fluorescence microscopic image using a thresholding algorithm to obtain a binary filter image, and making an overlay of the binary and crude filter image to determine the average grey value, standard deviation and surface area of individual cells, and wherein the nucleic acid content is calculated on the basis of the following equation: nucleic acid content = log standard deviation per microbial cell log average grey value per microbial cell (iii) classifying based on said at least first and second parameter said cell into one of the following categories: Viable cultivable cells with a nucleic acid content value between ≥0.1 and 1.0 and extent of stretching of the cell value between ≥1.0 and 10 μm 2, Viable non-cultivable cells with a nucleic acid content value of ≥-0.2 and extent of stretching of the cell value of ≥0.5 μm 2 minus Viable cultivable cells, Most likely dead cells with a nucleic acid content of <1.0 and extent of stretching of the cell value of <0.5 μm 2; and Viable cultivable cells with a nucleic acid content value between ≥0.1 and 1.0 and extent of stretching of the cell value between ≥1.0 and 10 μm 2, Viable non-cultivable cells with a nucleic acid content value of ≥-0.2 and extent of stretching of the cell value of ≥0.5 μm 2 minus Viable cultivable cells, Most likely dead cells with a nucleic acid content of <1.0 and extent of stretching of the cell value of <0.5 μm 2; and (iv) calculating the ratio of the amount of viable cultivable cells, viable non-cultivable cells and most likely dead cells in a microbial sample.