Herein, we have tried to review various routes of synthesis of nanoparticles. Then emphasis has been given on biological route of synthesis of nanoparticles where we discussed synthesis of nano-silver using algae, bacteria, plants, fungi etc. Also the chemical positions and possible traditional uses of the plants are enlisted. The use of plant extract for making nanoparticles is inexpensive, easily scaled up and environmentally benign. It is especially suited for making nanoparticles that must be free from toxic contaminants as required in therapeutic applications. Then at the end we discussed the toxic effects of nanoparticles.