By inserting metallocatalysts (such as platinum, osmium, or ruthenium) at the reducing site of photosystem I (PSI), electrons that emerge from PSI can be channeled to various redox reactions that could potentially produce fuels and chemicals (such as H-2 and CH4, and so forth) instead of NADP(+) reduction, as in natural photosynthesis. We have recently developed a technique to photoprecipitate metallocatalysts in situ at the reducing site of PSI in thylakoid membranes, using water-soluble hexachloroplatinate, hexachloroosmiate, and hexachlororuthenate at biological temperature and neutral pH. This technique combined with "rewiring" of photosynthesis is a potentially important new field of biometallocatalysis. Potential applications of biometallocatalysis will be addressed in this article.