This 1907 postcard reflects the format of its day; later that year, US postcard regulations would change where writing would hence forward be allowed on the reverse, instead of on a reduced photo side, as portrayed here.
This scan doesn't show it well, but the message is to one Robert E. Jennings of Menominee, Michigan from his Aunt Addi. She writes: "Hello Robert, why don't you write? You know we like to get letters. P.S. Edith says, when are you going to send the puppy?"
Today, Aunt Addi would have texted Robert, or perhaps email him. But still, there's nothing like sending familial guilt, whatever the media and whatever the era.
And as for the P.S., how DOES one get a puppy from Menominee to Menasha in 1907?