How find NumObjects filed like PixelIdList in program separately?

CC = bwconncomp(BW)
 CC =  
    Connectivity: 8    
    ImageSize: [3 3]
       NumObjects: 2
     PixelIdxList: {[1]  [2x1 double]}

the PixelIdxList field is a cell array with the indexes of coordinates for each region. The length of each array is the size of each region:

>> numPixels = cellfun(@numel,CC.PixelIdxList)
numPixels =
     1     2

[Guillaume]

Can you please be a bit clearer about what you're asking. It looks like you posted an excerpt from the doc and that's all.