100 um
100 Micron100 Micron's = 0.1 millimeter, about the width of a human hair.
the Oocyte is the largest human cell and can be seen by the naked eye. more information on the Oocyte: http://en.wikipedia.org/wiki/Oocyte
A particle is an atom which cant be seen by the naked human eye, everything is made up of: in solids; gasses and liquids. Each atom contains electrons, protons and neutrons, which is what gives each particle its properties. Solids tend to have more compact particles where as gasses have less.
the human heart can be seen with the naked eye if chest is open
Macroscopic things which could be seen by naked eye and under visible wavelength of light are considered opposite to Elementary particles !
You can see the Thorax and the Abdomen in the Torso
"microscopic" Naked = The average human eye, without the use of any artificial aids like, glasses, microscope, telescope etc.
A single fungus organism cannot be seen with the human eye, but a fungal colony, such as a mushroom or jock itch, certainly can be.
One theory is that amoebas are really, really tiny, and that the human eye is unable to magnify the recieved images to see them. Other theories state that amoebas don't exist, are invivisible and have poor comunication skills.
Naturists or Nudists like to be naked but not seen by outsiders. Exhibitionists like to be seen by all.
No human has ever seen the face of God and no can see him unless He wants someone to see Him.
Mercury, Venus, Mars, Jupiter, and Saturn can be seen with the naked eye.