Raw data for „X-ray studies bridge the molecular and macro length scales during the emergence of CoO assemblies“ TEM and SEM SEM image of CoO assemblies after 90 min TEM images of CoO assemblies after 5, 10, 15, 20, 40, 60 and 90 min HR-TEM images of CoO assemblies after 90 min ED patterns of CoO assemblies after 10, 15 and 20 min HERFD-XANES In situ spectra for the CoO synthesis at 160°C were recorded at beamline ID26 at the European Synchrotron Radiation Facility (ESRF), Grenoble, France. Using a Si (111) double crystal monochromator, the incident energy was varied from 7.70 to 7.78 keV. The emitted fluorescence was measured with an emission spectrometer in Rowland geometry with five Si (531) analyzer crystals aligned at the Bragg angle of 77°. HERFD-XANES spectra were recorded in continuous scan mode every 80 s with average energy steps of 0.05 eV. The data set consists of one file containing a sequential set of energy scans, representing the pre- and main edge regions of the HERFD-XANES spectra. Important column identifiers: incident energy: “arr_hdh_ene” incident intensity: “I02” fluorescence intensity: “apd” X-ray total scattering Data was taken at beamline P21.1 of PETRA III at Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany. Diffraction patterns were recorded every 10 s at an X-ray energy of 102.92 keV (λ = 0.121 Å) with an XRD1621 detector (Perkin Elmer Inc., USA) with a pixel size of 200 × 200 μm² and a sample-to-detector distance of 0.411 m. The dataset consist of in situ data set of CoO nanoassembly synthesis at 160°C in situ data set of CoO nanoassembly synthesis at 140°C ex situ samples prepared at 160 °C at different times commercial reference compounds in powder and 0.1 M BnOH solution data format: 2D scattering patterns in .tif format The total scattering data is split into individual archives for the above subsets. SAXS and PXRD data set “laboratory_SAXS_data”: Data were recorded with the laboratory molybdenum anode microfocus X-ray setup at LMU, Munich. SAXS data are multiple successive 20 min exposures. Transmission data are 10 s exposures with the beamstop removed. data format: .tif detector images recorded with a Dectris Pilatus 300K. X-ray wavelength: 0.71075 Angstrom Calibrant for sample-to-detector distance, beam center and detector tilt: Silver behenate (AgBeh) data set “synchrotron_SAXS_data”: Data were recorded at beamline P03 at PETRA III, DESY, Hamburg. Data are recorded separately at a long and a short sample-to-detector distance. At the long distance, the exposure time is 5x0.1s. At the short distance, the exposure time is 1x0.5s. data format: .cbf detector images recorded with a Dectris Pilatus 1M. X-ray wavelength: 0.961 Angstrom Calibrant for sample-to-detector distance, beam center and detector tilt: Silver behenate (AgBeh) data set “laboratory_PXRD_data”: Data were recorded with the laboratory molybdenum anode microfocus X-ray setup at LMU, Munich. The overlap for stitching is 10 px in both horizontal and vertical direction. The recording sequence is 01 02 07 03 04 08 05 06 09 10 11 12 13 14 15 with 3 images at each position, to take the median. The exposure time per image is 1200 s. For LaB6 the sequence is 01 02 03 04 05 06 07 08 09 10 with 5 images at each position, to take the median. The exposure time per image is 300 s. data format: .tif detector images recorded with a Dectris Pilatus 100K. X-ray wavelength: 0.71 Angstrom Calibrant for sample-to-detector distance, beam center and detector tilt: Lanthanum hexaboride NIST SRM 660c (LaB6)

Acknowledgements This work was supported by the European Research Council within the project LINCHPIN (grant no. 818941), by the Bundesministerium für Bildung und Forschung (BMBF) via project LUCENT (grant no. 05K19WMA), by the Bavarian State Ministry of Science, Research, and Arts through the grant "SolarTechnologies go Hybrid (SolTech)", by the Cluster of Excellence "The Hamburg Centre for Ultrafast Imaging" of the Deutsche Forschungsgemeinschaft (DFG) - EXC 1074 - project ID 194651731, by the Cluster of Excellence "CUI: Advanced Imaging of Matter" of the DFG - EXC 2056 - project ID 390715994, by the DFG via project ID 201269156-SFB1032, and by the São Paulo Research Foundation (FAPESP, grant no. 2018/08271-7 and 2016/25267-8). We thank Dr. Lucia Amidani, Dr. Rafal Baran, Dr. Roelof van Silfhout, Dirk Detollenaere, Florian Ledrappier, Martina Ober, and Ludwig Hendl for supporting the X-ray measurements and laboratory experiments, Andreas Kornowski, Andrea Koeppen, Stefan Werner and Susanne Kempter for TEM imaging and ESRF, ID26 for beamtime allocation. We acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of this research were carried out at PETRA III and we would like to thank Prof. Stephan Roth, Dr. Matthias Schwarzkopf and Dr. Martin Roelsgaard for assistance in using beamlines P03 and P21.1.