What is this secret that everyone knows about? It’s the secret of being able to satisfy thirst after being thirsty, the secret of how a mango tree grows, and the secret of how the trace left by soil after playing disappears without a trace. Discover this secret! Learn how you can keep this secret with you throughout your life. The Green House… A series of easy-to-read books designed for young children, helping them to take responsibility for their families, their environment, and the world around them.