As plants develop, they follow distinct growth and movement patterns, called tropisms. These directional movements occur in response to environmental stimuli, such as gravity, light and touch. You can demonstrate a plants ability to bend towards the light by observing the way a sunflower will turn its flower towards the light, or the way plants will bend towards the light if they are away from a window or on the edges of a grow light. This is often known as heliotropism.
You can take this one step further and create a maze from a cardboard box for a bean to grow towards the light. Cut an opening at the top of the box to allow light through, and use cardboard strips within the box to block the direct path to the light. Observe as your plant navigates these obstacles to find the light!