Phosphorus, the second element of the fifth group of the periodic table, is heavily embroiled in the energy metabolism of living beings. This element, together with oxygen, forms phosphoanhydride bonds, one of the most energy-rich linkages in biomolecules. The most well-known occurrence of these bonds is within the triphosphate chain of ATP. More recently, besides ATP, increasing attention has been paid to a much more energy-rich molecule, consisting of long chains of phosphate units. This inorganic polyphosphate (polyP) acts as an energy storage and donor in prokaryotes and higher eukaryotes (animals and humans), particularly within the extracellular space. It turns out that this unique biopolymer, prepared in a bioinspired way, has great potential for regenerative medicine applications.