The invention includes methods of forming layers comprising epitaxial silicon. In one implementation, an opening is formed within a first material received over a monocrystalline material. Opposing walls, of a second material, are formed within the opening which are laterally displaced inwardly of the opposing sidewalls, a space being received between the opposing walls and the opposing sidewalls, with monocrystalline material being exposed between the opposing walls within the opening. A silicon-comprising layer is epitaxially grown from the exposed monocrystalline material within the second material-lined opening. Other aspects and implementations are contemplated.