  Integrated sensing and communications (ISAC) has opened up numerous
game-changing opportunities for future wireless systems. In this paper, we
develop a novel ISAC scheme that utilizes the diffusion model to sense the
electromagnetic (EM) property of the target in a predetermined sensing area.
Specifically, we first estimate the sensing channel by using both the
communications and the sensing signals echoed back from the target. Then we
employ the diffusion model to generate the point cloud that represents the
target and thus enables 3D visualization of the target's EM property
distribution. In order to minimize the mean Chamfer distance (MCD) between the
ground truth and the estimated point clouds, we further design the
communications and sensing beamforming matrices under the constraint of a
maximum transmit power and a minimum communications achievable rate for each
user equipment (UE). Simulation results demonstrate the efficacy of the
proposed method in achieving high-quality reconstruction of the target's shape,
relative permittivity, and conductivity. Besides, the proposed method can sense
the EM property of the target effectively in any position of the sensing area.
