Why is this the answer?

The answer is memory because it is like a wonderful, magical picture book that lives inside your mind and travels with you every single day. A memory is a special kind of thought that lets you go back in time without needing an actual time machine. It is one of the greatest secrets your brain keeps just for you. Let's look closely at the riddle's clever clues. The first part asks, "What can bring back the dead." This is a tricky clue, but it means that if someone you know and love is no longer with us, a special memory helps you remember their face, their voice, and the fun things you did together. It is like they are still right there with you for a little moment when you remember them clearly. The riddle also says a memory can "Make us cry, make us laugh." If you remember a super funny joke you heard last week or a silly thing your pet did, that memory is so powerful it makes you laugh right out loud, even if you are alone. And if you remember a moment that felt sad or a little difficult, that memory can make you feel a little teary. Our memories hold all of our big feelings, both happy ones and sad ones. Then there is the line, "make us young." When you sit quietly and remember your first day of school, or when you were a tiny baby taking your very first steps, that memory takes you all the way back. It makes you feel young again just by thinking about what it was like when you were smaller. Finally, a memory is "Born in an instant yet lasts a life time." When you are having a fun time right now, that moment is happening, but as soon as it is over, a picture of it is instantly saved inside your brain. That saved picture, the memory, stays with you for your whole life. It is a treasure you can open and look at any time you want, and that is why memory is the perfect answer to this wonderful old riddle.