python just import fails but works with from

Why does this not work:

import matplotlib.pyplot as plt
import os
import skimage
camera = skimage.io.imread(os.path.join(skimage.data_dir, 'camera.png'))
#plt.show(io.imshow(camera))

But using from skimage import io does. So this works:

import matplotlib.pyplot as plt
import os
import skimage  # I still need to import skimage to get the data_dir
from skimage import io
camera = io.imread(os.path.join(skimage.data_dir, 'camera.png'))
#plt.show(io.imshow(camera)) 

I thought

import skimage
skimage.io."something"

Was equivalent to

from skimage import io
io."something"