In 1934, science-based toy manufacturer the A.C. Gilbert Co. began marketing a line of toy microscopes to teach children about photographic images. Surprisingly advanced for a toy, Gilbert's scope included a turret allowing three different levels of magnification, which came in handy while peering at insects. (The set included bees, flies and fleas, while instructions encouraged children to collect new subjects on their own.) The set was viewed as reasonably sophisticated and was praised for its coverage of microscope lab-procedure fundamentals, but its lengthy manuals read more as college texts than toy instructions.