When a high-energy projectile collides with a nucleus, a number of energetic charged and uncharged particles are produced. The emergence of these fast particles known as shower and grey particles in the nuclear emulsion occurs in a very short time after the impact of the projectile. Grey particles, which are emitted from the target nucleus, are mostly the recoil protons with an admixture of low energy pions. After the emergence of fast particles, the nucleus remains excited for a long time on nuclear time scale.