# MATLAB: What is the meaning of 28x28x3 in .mat file

.mat file

Hi, I save a colour image in .mat file format and realise that the variable is in array 28x28x3. 28×28 is image dimension, but I have no idea on what the "3" meant. I guess it is related to colour. Can anyone explain on this ?
here is the code that I type
• pic1 = imread('image_0001.jpg');
• save('BothPics.mat', 'pic1');

[rows, columns, numberOfColorChannels] = size(pic1)