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 of the intensity 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.