"Who is Einstein?" "Maria, you don't know Einstein? Albert Einstein was the greatest genius of all time. He completely revolutionized physics and our understanding of space and time." My uncle points to a photo on the wall. It shows a man with messy white hair sticking his tongue out at us. "Is that Einstein?" I'm speechless. "He looks like Struwwelpeter!" Maria and her friend Victor take a time trip to the past and meet Albert Einstein at his summer house in Caputh. A great opportunity to clarify many questions: Do felt slippers survive a time travel? Can you really understand the theory of relativity? How do you solve the twin paradox? Can Einstein make a phone call with a mobile phone? How do you explain the internet to someone who comes directly from the past? And what does the word 'relative' actually mean? A book for people aged 6 and up.