During in-situ observations in liquid-phase transmission electron microscopy (LP-TEM) the application of different dose rates may considerably alter the chemistry of the studied solution and influence processes, in particular crystallization and growth pathways. While many processes were studied in LP-TEM in the last decade, extent of the beam influence on the processes is not always understood and experiments are rarely compared to corresponding bulk systems under radiation. A conventional Cs-137 GammaCell is a bulk counterpart to a nanoscale LP-TEM cell and applies up to 6 orders of magnitude lower dose rate. In this study, we used the processes of CeO2 crystallization from CeCl3 x 7H2O aqueous solution induced by γ-radiation as a model reaction, for which we proposed the mechanism of radiolytic formation of metal oxides. Hydroxyl radicals produced upon gamma radiolysis of water oxidize highly soluble Ce3+ to sparsely soluble Ce(IV) which forms CeO2 upon hydrolysis. It was found that the primary CeO2 particles are formed inside amorphous hydrated Ce(IV)-hydroxides phase, confinement in this phase guides mutual alignment of the primary particles to mesocrystals. In-situ LP-TEM investigations using homogeneous illumination showed that the higher dose rate in LP-TEM does not modify the non-classical crystallization pathway. Furthermore, primary particles and aggregates are of the same size as grown in the gamma-cell. This is surprising given the fact that for radiation-induced synthesis of metal nanoparticles (radiolytic reduction), the particle size displays strong dose rate dependence. However, the precursor is converted significantly faster in LP-TEM as an effect of higher radical concentrations caused by a higher dose rate. Moreover, we studied the influence of concentration gradients on the growth in LP-TEM by changing the illumination from spatial and temporal homogeneous to periodically varying (scanning transmission electron microscopy (STEM)). The growth mechanism modifies from isotropic mesocrystal-like formation to diffusion dependent dendritic growth, which is coherent with previously reported dendritic growth of Fe-oxides in organic solvents inside LP-TEM.