PROMETHEUS aims to carry out an in-depth investigation of the nature of mineral structures such as silica biomorphs and chemical gardens and the role of mineral self-organization in extreme alkaline geological environments. The results will impact our current understanding of the early geological and biological history of Earth by pushing forward the unexplored field of inorganic biomimetic pattern formation. The ambitious research programme will include the development of high-end methods and instruments for the non-intrusive in situ characterization of geochemically important variables, including pH mapping with microscopic resolution, time resolved imaging of concentration gradients, microscopic fluid dynamics and characterization of ultraslow growth rates.