Hi Anjali Shrivastava . Are your original images in jpg format? It's always best to have them in an uncompressed format (like tiff) when quantifying. With that said, you will need to work with an 8-bit image (the one you posted is RGB). Go to Image>Type>8-bit to do the conversion. You can then threshold your image using one of the automatic algorithms. You probably need to make the image binary so that you can use the watershed operation. Then you can Analyze Particles (make sure you set measurements to include area and/or perimeter). You can also try machine learning via Trainable Weka Segmentation.

Here are some videos you can check out re thresholding and measuring size:

https://www.youtube.com/watch?v=XkGK7T12OiM

https://www.youtube.com/watch?v=5b7x2qx1FF0

https://www.youtube.com/watch?v=65kd_jK1xQM

In addition to Johanna Marie Dela Cruz comment: for analysis you need an image with particles on it. I do not see particles on attached image.

In addition to Vladimir Dusevich and Johanna Marie Dela Cruz's comment: for a good analysis, you need the high resolution of your image. Also, it is very difficult to distinguish the matrix material and porosity in the attached image.

Does the black phase represent pores?

Best kinds

IDIR

Thanku, Thanku everyone Vladimir Dusevich , Idir Abdelhek Johanna Marie Dela Cruz