A novel processing route for fabricating cellular and microcellular ceramics with controllable open-cell content has been developed. The proposed strategy for producing cellular and microcellular ceramics involves: (i) development of desired foamable polysiloxane-polyolefin blends by using a compounder element, in which the polyolefin phase is uniformly dispersed in the polysiloxane matrix, (ii) foaming the obtained blends by implementing the thermodynamic instability principle to produce a cellular or microcellular ceramic precursor structure, and (iii) completing the organic-inorganic transition without sacrificing the obtained cellular or microcellular structure and inducing open-channels in the cell walls by burning out the sacrificial dispersed polyolefin phase at elevated temperatures. By controlling the viscosity of the dispersed polyolefin phase, the polyolefin concentration and compounding parameters, the polysiloxane-polyolefin blend morphology can be varied. Furthermore, plus a deliberate control of foaming and pyrolyzing parameters, the foam morphology and open-cell content of produced cellular and microcellular ceramics can be adjusted. In this paper, the technique to get a desired cellular and microcellular ceramic precursor structure is demonstrated. The deliberate pyrolysis technique to complete the organic-inorganic transition and the mechanical properties of the obtained microcellular ceramics will be discussed in another paper.