The invention includes methods of utilizing supercritical fluids to introduce precursors into reaction chambers. In some aspects, a supercritical fluid is utilized to introduce at least one precursor into a chamber during ALD, and in particular aspects the supercritical fluid is utilized to introduce multiple precursors into the reaction chamber during ALD. The invention can be utilized to form any of various materials, including metal-containing materials, such as, for example, metal oxides, metal nitrides, and materials consisting of metal. Metal oxides can be formed by utilizing a supercritical fluid can be utilized to introduce a metal-containing precursor into reaction chamber, with the precursor then forming a metal-containing layer over a surface of a substrate. Subsequently, the metal-containing layer can be reacted with oxygen to convert at least some of the metal within the layer to metal oxide.