In this investigation, learners plant seeds in a 2-liter bottle filled with soil that is connected to a water source below. Over the next few weeks, learners observe how the plants grow. The investigation is open-ended, with suggestions for variables to change and indicators to measure, such as pH of the soil and water. Instructions are given for performing a salt pollution experiment as one possibility. The activity comes from a printed book that is also available in Spanish, though the Spanish version is not available online.