All-sky map of the gamma-ray annihilation signal of our Galaxy. Pointlike sources indicated by arrows show the contributions from microhalos less than 1 pc from the observer and with flux larger than 0.03 photons m ⁻² s ⁻¹ sr ⁻¹. Here, we assume that the number of photons per annihilation is N _γ = 30, the interaction cross section of dark matter is σ v = 3.0 × 10 ⁻²⁶ cm ³ s ^-1, and the mass of dark matter particle is m _χ = 100 GeV. The flux of the integrated emission of microhalos in the galactic center is 1.40 photons m ⁻² s ⁻¹ sr ⁻¹. The flux of the most brightest microhalo is 0.069 photons m ⁻² s ⁻¹ sr ⁻¹. The flux needed for a 10σ detection for Fermi is ~0.4 × 10 ⁻⁶ photons cm ⁻² s ⁻¹ for low Galactic latitude and is ~0.1 × 10 ⁻⁶ photons cm ⁻² s ⁻¹ for high Galactic latitude (Abdo et al. 2009a). The angular resolution of Fermi is about 0.1 deg for energies above 1 GeV.