Around 9 to 12 months, children begin to explore the world using their senses of touch, taste, sight, and hearing. They develop initiative while still wanting a caregiver nearby for safety. Language skills start emerging as they understand simple words and babble, saying sounds like "mama" and "dada." They also communicate through gestures, facial expressions, sounds, and body movements in response to others. During this time, children learn to crawl which helps strengthen their muscles for walking.