Since ancient time silver and silver based compound have been used as a powerful antimicrobial agent in medicine. Discovery of antibiotics pushes the silver away from medicine and pharmaceutical sciences. By emerging resistance strains and reducing the efficiency of antibiotics, silver became point of attentions again, but in a novel form of silver nanoparticles (AgNPs). AgNPs are the most effective and powerful novel antimicrobial with ancient roots. Chemical synthesis is one of the first techniques for synthesis of AgNPs. In this technique silver ions reduced to AgNPs by using chemical reducing agents such as sodium borohydride (NaBH4) and sodium citrate (Na3C6H5O7). Later investigations have shown that biological molecules from living organisms such as bacteria, fungi, algae, and plants can also be used as more safe and in some cases sheep reducing agent for biosynthesis of AgNPs.