I cannot claim any part of this activity; in fact, I found it on the Internet somewhere, and unfortunately don't remember where, or I'd give credit where credit is due. Basically, I had students "build something" using mini-marshmallows and toothpicks, then draw their construction using circles for the marshmallows and lines for the toothpicks. The drawings were done with pencil, and then traced with colored markers. Very easy directions for what turned out to be not so easy of a task.
I quickly modeled the whole process, not only the building part but especially the drawing part. I did a lot of "thinking aloud" to give students an idea how I decided to draw my structure. I talked about the toothpicks going in different directions, for example; "hmm... this one sticks out on this side, and this one over here goes the opposite direction and kind of down, making kind of a triangle shape...." so they would take the time to try to replicate their structures as best as they could.
I had each student count out twenty marshmallows and provided a paper plate full of toothpicks for each table. I asked them to use as many of their marshmallows as they could, because I didn't want the sculptures to be too small. As they worked, I made some interesting observations. The building with marshmallows and toothpicks part was pretty easy for most, although there was some problem-solving for students whose structures were getting a little tall. Some students finally just laid their sculptures down sideways on the table because they had a hard time getting them to stand up. But what was really interesting was watching students translate their three-dimensional sculptures to two-dimensional drawings. Getting the depth was very, very tricky.
After they drew and traced their structures, students were allowed to eat their marshmallows, including the ones that made up their sculptures. Lucky for me, one little girl did not like marshmallows so I put her sculpture, a very complicated, organic-looking thing, on a table off to the side. In the following class an hour later, her twin sister built a very similar sculpture; her drawing looked remarkable like her twin's sculpture. Interesting.....