Ferrofluid is a colloidal liquid made of particles less than 10 nanometers in diameter. When exposed to to a magnetic field, the nanoparticles form regular patterns of peaks and valleys. You can demonstrate magnetic fields for your students in a very visual way. Included: 50mL Ferrofluid WARNING: This is not a toy, this product is intended for scientific use by ages 13 and up. DOT Info: Non-regulated