Hi, Thank you for your response I appreciate it. I have calculated the volume by AVIZO software and the volume is a 8 digited number. I do not know what units it has used for the calculation. I know that the pixel size is 6.5um. how do I convert these 8 digited numbers to mm or um? I do understand that for 3D measurements each voxel will represent 6.5*6.5*6.5um^3. I will appreciate any advise on this. Thanks.