This is a little different for this blog, because it is not actually a photograph. It is a late 19th century embossed lithographic die-cut showing a very young girl in a fancy dress and bonnet. The back of it is completely covered by verbiage, touting the benefits and modernity of Pearline Soap Powder.
Trade cards were little bits of advertising, frequently no larger than a present day business card, given away free, or perhaps with a purchase of a certain product. Some came in series or sets and the people who inhabited the 19th century apparently loved to collect them. There are still tons of them about, most are not very expensive, and some (like, in my opinion, this one) are quite nice.