How do I remove a photo from a picture frame glass?

I have a photo of my children, when they were younger, and the photo has been in the picture frame for quite some time.
The photo seems to be stuck onto the glass, in the picture frame, and I can't get the photo away from the glass. Does anyone have an idea how I can detach the photo from the glass without destroying the photo?

?2016-05-07T11:15:25Z

Just soak it in some warm water. When the image was made at the photo lab, the image was washed in a water bath and then dried. So you don't have to worry about the water damaging the image in any way. However this is assuming that the image was not printed on an ink-jet printer which would most definitely get ruined if submerged in water.

If you're unsure of this, I would take a photo that you don't care about that was printed on the same paper and submerge it into warm water for 30 minutes.

?2016-05-06T21:11:05Z

http://www.scanmyphotos.com/blog/2015/05/remove-photo-stuck-glass-ideas.html
... I have no idea if that works; he doesn't either. Food for thought, however ...