We present the recent developments of $B$-meson light-cone distribution amplitudes (LCDAs) including their definition, classification, evolution, equations of monition (EOMs), and modeling. By making use of these recent developments, one particular decay channel $B\to\gamma\ell\nu_\ell$ is discussed in detail with the most accurate theory predication to date for its branching ratio which has been used to extract the value of $\lambda_B$ --- the most important $B$-meson parameter in exclusive decays.