This summer we went to visit my sister's office and see some of the labs in her building - she's finishing up her doctorate at a Big 10 uni. While there, we got super lucky because there were tons of lab supplies in the hall with signs saying "free." So we loaded up the stroller! Beakers, test tubes of all types and sizes, corks, rolls of graphing paper, test tube holders, long skinny measuring tubes, etc. DS4 was so excited! So we have all of that, plus magnifying glasses, safety glasses, and household items such as balloons, marbles, rubber bands, etc. I also have bulb holders, wire, and slides on the way. I'm planning to get DS a microscope for Christmas. I need to get better magnets.