There's a saying that a watched pot never boils. You could also say that a watched plant never grows - that is, unless it's being watched by a laser-wielding, 3D plastic sculpture-making robot.
David Bowen's "Growth Modelling Device" uses a circular rig to scan an onion in once a day and then a "fuse deposition modeller" generates a plastic sculpture of that scan. When the model is a done, a conveyor belt burps into action, moving the model out of the way and making room for the next day's creation.
What you end up with is a visual record of the onion's growth over the course of a few weeks - with no tears involved!