Abstract: he formation of monodispersed hexagonal T grain of silver bromide has been observed and investigated by means of analytical electron microscopy. The morphological observation of the grains shows clearly that: the formation of tabular grain is a gradual evolution process. At the early nucleation stage the grains are spherical, after definite time the spherical grains become tabular. The size distribution indicates that at the nucleation stage two district populations (grain size distribution peaks) appear on the size distribution curve. Between these two peaks there is a critical size. Grains of size being larger than that critical size tend to grow and become tabular, while the others smaller than critical size is apt to desappears or become small. The values of n of silver halide cluster at the early nucleation stage has been estimated and discussed.

Key words: silver halide emulsion, nucleation, T-grain