In photosynthesis, solar energy is converted into electrons, photosynthetic electrons (PEs), and they are utilized for survival of plant cells or stored in the form of carbohydrates. Due to high conversion efficiency of photosynthesis ~ 100 %, various efforts have been made to collect photosynthetic electrons. We have developed various nanoelectrode systems to understand and estimate the feasibility of direct extraction of PEs both from living algal cells and isolated thylakoid membranes from spinach leaves. In this talk, nanoelectrode systems for PE extraction will be introduced and their performance will be discussed. Finally, how this PE extraction can be developed into a power system in a form of bio-photo-electrochemical cell, and their feasible application for self-powered sensor systems will be discussed.