Formation of a spherical halo from a specific cosmological perturbation. Top panel: evolution of number densities of H, D, and He in the top-hat halo with k = 80 Mpc (M_h = 1.26 × 10⁻⁶ M_⊙) and initial amplitude of adiabatic scalar perturbation δ_r = 1.5 × 10⁻⁴ at z = 10⁸). Bottom panel: evolution of the temperature of CMBR (green line) and kinetic temperature of the top-hat halo with adiabatic heating (dark line) and virial temperature (8; red line).