Steganography means hiding secret data/msgs inside the bits of the image matrix (as it would be harder to discover they r used as a transferring media in the first place)
The most naive approach would be to just store in the grades of a color accuracy like Black in a high resolution image for example; such naive approaches can be easily discovered by any resize/rotate of the image.
More complicated approaches started to appear in 2000-2005 maybe,
I think this one is also about steganography although not in the title
"Hiding Secret Messages in Huffman Trees"
I even recall articles after 9/11 suspecting that Osama Ben Laden was sending encrypted msgs to his allies thru his broadcasted videos using steganography ( I remember an article entitled "Could Ben Laden be a Steganography Master"?
Anyways, I don't think the topic flourished as a research area afterwards.
I just Googled it now, there are books & explaining dated to 2011, but almost nothing new except 2 papers
One in 2019
"An efficient steganographic technique for hiding data"
One in 2015
"Steganography for inserting message on digital image using least significant bit and AES cryptographic algorithm"
(you can find more references inside those papers)