In situ high-resolution transmission electron microscopy experiments were applied to examine the nano-scale solidification process of boron-doped silicon from the liquid state. Fine particles of the specimen were first heated up to the melting temperature using a TEM heating-holder, and then gradually cooled across the melting temperature. The specimen was observed nearly along  direction. The lattice fringe of (220) plane was observed during solidification, and this part combined with the other liquid part to make a twist boundary. The angle between the (220) planes of these two crystal grains was close to the rotation angle of the (001) Σ5 twist boundary.