Black phosphorus intercalation compounds (BPICs) with alkali metals (namely: K and Na) have been synthesized in bulk by solid‐state as well as vapor‐phase reactions. By means of a combination of in situ X‐ray diffraction, Raman spectroscopy, and DFT calculations the structural behavior of the BPICs at different intercalation stages has been demonstrated for the first time. Our results provide a glimpse into the very first steps of a new family of intercalation compounds, with a distinct behavior as compared to its graphite analogues (GICs), showing a remarkable structural complexity and a dynamic behavior. Black to the future: The bulk intercalation of black phosphorus with alkali metals (namely: K and Na; black spheres) has been developed, showing a complex dynamic structural behavior. By in situ Raman spectroscopy and DFT calculations straightforward fingerprints for the identification of black phosphorus intercalation compounds (BPICs) have been demonstrated.