A method for characterizing a state of adhesion of at least one particle , via a system comprising a spatially coherent light source and a matrix photodetector , the particle(s) , such as cells, being contained in a liquid medium , the liquid medium being delimited by a transparent surface , the particle(s) being able to adhere to said transparent surface , the matrix photodetector being able to measure the distribution (X) of the intensity (I) of at least one diffraction pattern , the method comprising the following steps: - illuminating the medium with the spatially coherent light source , - acquiring at least one image (I 1 (x, y), I n (x, y)) by the matrix photodetector , the image (I 1 (x, y), I n (x, y)) being formed by radiation transmitted by the illuminated medium and including at least one elementary diffraction pattern , each elementary diffraction pattern corresponding to waves diffracted by a particle during the illumination of the medium , - computing , from at least one acquired image (I 1 (x, y), I n (x, y)) and for at least one particle , a primary indicator characterizing the state of adhesion of the particle to the transparent surface , the method being characterized in that it further comprises the following step: - computing , from at least one acquired image (I n (x, y)) and for at least one particle , at least one secondary indicator (S, K) characterizing the spreading of a cell having adhered to the transparent surface, said or each secondary indicator (S, K) being distinct from the primary indicator, at least one computed secondary indicator (S, K) depending on a moment of order M of the intensity at the center of a corresponding diffraction pattern , M being an integer with a value greater than or equal to 3; and further the time derivative (dS/dt, dK/dt) of at least one computed secondary indicator (S, K) for detecting the spreading of the cell having adhered to the transparent surface. - illuminating the medium with the spatially coherent light source , - acquiring at least one image (I 1 (x, y), I n (x, y)) by the matrix photodetector , the image (I 1 (x, y), I n (x, y)) being formed by radiation transmitted by the illuminated medium and including at least one elementary diffraction pattern , each elementary diffraction pattern corresponding to waves diffracted by a particle during the illumination of the medium , - computing , from at least one acquired image (I 1 (x, y), I n (x, y)) and for at least one particle , a primary indicator characterizing the state of adhesion of the particle to the transparent surface , - computing , from at least one acquired image (I n (x, y)) and for at least one particle , at least one secondary indicator (S, K) characterizing the spreading of a cell having adhered to the transparent surface, said or each secondary indicator (S, K) being distinct from the primary indicator, at least one computed secondary indicator (S, K) depending on a moment of order M of the intensity at the center of a corresponding diffraction pattern , M being an integer with a value greater than or equal to 3; and further the time derivative (dS/dt, dK/dt) of at least one computed secondary indicator (S, K) for detecting the spreading of the cell having adhered to the transparent surface. <EOS>