The case of the Ni50Co50-mixture with its counter-intuitively long reaction time (ESI: Figure and S2F) arose the question of how the reconfiguration of the precursor to a final crystalline unit is accomplished in this system. For this purpose, the Ni50Co50-system was also studied with in-situ scattering accompanied by pH measurements to observe potential differences in their crystallization pathway. In theory, both metals can be incorporated into the crystalline phases considered to form solid solutions . However, upon precipitation from aqueous solution, the starting aqueous ionic concentrations and the final metal composition in the crystals differ significantly. Therefore, the occurring crystalline phases are named, M-struvite and M-octahydrate with M = NixCo1-x. In the mixed system, surprisingly, the overall time scales of the entire formation process got extended significantly, and in addition, more complex transformation pathways were observed, including several crystalline phases. Firstly, even faster than in the case of the Nisystem, M-struvite formed within t = 100 s as observed in diffraction and correlating well with the occurrence of q -4 interfaces at low angles. Simultaneously, co-existing amorphous phases scattered in the intermediate q region in a "knee" region at around 0.3 nm -1 to 1 nm -1 similar as in the pure Co-system (Figure and Figure ). These scattering features of the amorphous phases evolved through time reaching an intensity maximum at t = 1300 s. In the time interval from 1300 s < t <1700 s, until the first formation of M-octahydrate, the signal at intermediate q decreased rapidly. In the time window from t = 1700 s -3700 s, the previously formed Mstruvite and the M-octahydrate crystals coexisted together. Here, the octahydrate's diffraction intensities increased further, indicative of a growing volume fraction of this phase, while the M-struvite crystals dissolved gradually as evidenced from the disappearance of the associated Bragg peaks. After t = 3700 s, M-struvite was dissolved completely resulting in a single-phase composition of M-octahydrate. Based on the pH curve, equilibrium was reached after the precipitation of M-octahydrate hinted by a drop of pH beginning at t = 6500 s finalized at t = 9000s, to reach a plateau value of 4.7. All significant events in the in-situ scattering of the Ni50Co50-experiment are summarized in selective time frames (ESI: Figure ). In the Ni50Co50 system, complex trends of the fitting parameter can be observed (Figure , ESI: Figure ). Firstly, at around t = 100 s, the sub-level parameters reached their maximum values (Gsub = 9 cm -1 , Bsub = 0.044 cm -1 and Rsub = 11 nm) indicative of reaching a maximum number of nucleating entities with several nm in size (ESI: Figure ). Due to the partial consumption of these building blocks in the Ni-struvite crystal formation, all sub-parameters decreased roughly by half until t = 400 s (Gsub = 4 cm -1 , Bsub = 0.033 cm -1 and Rsub = 5.5 nm, ESI: Figure ). In contrast, the hierarchically higher-level parameters G, B, and Rg declined rapidly to a minimum value (G = 200 cm -1 , B = 0.005 cm -1 and Rg = 24 nm). Concurrently, the Rsub of the nucleating entities grew progressively by around 15% to around 7 nm until t = 1900 s (Figure ). When the dissolution of M-struvite (MIS) started, all sub-parameters declined to a global minimum. As Rsub is most likely representing the radius of the smallest characteristic entity, it also declined to a constant plateau value. It is just affected by Bsub (Gsub ≈ 0 cm -1 ) and, therefore, the signal extinguishes after their consumption. Consequently, the evolution and absolute values of Rg are congruent and in the same length scale to the sizes of the spherical building units observable in the TEM micrographs. Due to the simultaneous co-precipitation of M-phosphate octahydrate (MPO), the higher-level parameters G and Rg increased to a plateau value with Rg = 32 nm and G = 580 cm -1 at around t = 3000 s. Most likely even larger particles form could not be quantified sufficiently well from the model as the lower q-range would be required. B is deviating from this trend as it is affected by Rg and Rsub (ESI: Supplementary Note 2). In sum, the fits of the in-situ SAXS data reflect the nucleation of the precursors, its entities and the transformation processes between them. The in-situ scattering data clearly demonstrate the coexistence of amorphous precursors and already formed crystalline phases in several time intervals.