Epitaxy of silicene-on-Ag(111) renewed considerable interest in silicon (Si) when scaled down to the two-dimensional (2D) limit. This remains one of the most explored growth case in the emerging 2D materials fashion beyond graphene. However, out of a strict silicene framework, other allotropic forms of Si still deserve attention for technological purposes. Here, we present 2D Solid Phase Crystallization (SPC) of Si starting from an amorphous-Si on Ag(111) in atomic coverage to gain a crystalline-Si layer by post-growth annealing below 450 °C, namely Complementary Metal Oxide Semiconductor (CMOS) Back-End-of-Line (BEOL) thermal budget limit. Moreover, taking benefit from the 2D-SPC scheme, we also managed to write crystalline-Si pixels on the amorphous-Si matrix. Our in situ and ex situ analysis show that an in-plane interface or a lateral heterojunction between amorphous and crystalline-Si is formed …