Royal College of Art graduate Pratik Ghosh has designed a home filtration system that's powered by herbs and purifies waste water from the kitchen. Drop by Drop houses plants under a glass dome. Pipes allow water to be added in to be purified, and later collected. The system is designed for grey water – which comes from washing machines, sinks and baths. A light within the dome triggers the plants to photosynthesise and transpire, so water is drawn through the roots and onto the leaves, where it enters the air as vapour. A pump controls the system's airflow and creates a vacuum to further expedite transpiration. The moisture is then drawn out of the dome, and condensed to form purified distilled water – which can have salt added to make it suitable for drinking. Drop by Drop also releases oxygen into the room. It is a biosphere wherein the five key factors necessary for efficient transpiration, namely warmth, wind, light, pressure and humidity, are maintained at an optimum level.