The general assumption that zeolite crystallization proceeds through solution-mediated transformation has been investigated in recent years, and the occurrence of heterogeneous nucleation and crystal growth has been established. It has been demonstrated that an amorphous phase forms the starting, material for the nucleation of zeolite. Imaging through high-resolution transmission electron microscopy (HR-TEM) and dynamic light scattering (DLS) has shown the existence of an amorphous phase prior to the nucleation and crystal growth phase. Crystal growth by reorganization of a hydrogel through solid-solid transformation has been suggested in the literature. Heterogeneous transformation in zeolite crystallization has led to the development of a dry process as opposed to the conventional hydrothermal process. In the dry process the hydrogel is dried and converted to crystals in the presence of water vapor (steam) or a mixture of vapors of water and organic structure directing agents. Efficient synthesis of several types of zeolites is reported, such as: NaY, ZSM-5, ZSM-35, ZSM-48, BEA, NU-1, Ti-NU-1, Al-PO4, EU-1, etc. The role of water in the dry synthesis is reviewed.