Visible light is the only kind of electromagnetic waves that are visible, however there are 7 types of electromagnetic waves, or we can call them electromagnetic radiations. Rank based on wavelength, from high to low, they are:
Radio wave
Microwave
Infrared Ray
Visible light
Ultraviolet Ray
X-ray
Gamma Ray
Notice that Gamma Ray has an extremely small wave length and can be as small as 1E-15 m.