Once upon a time, there was a very smart scientist named Dr. Smith. He loved to invent things and one day, he created a time machine! He was so excited to travel through time and see all the amazing things that happened in the past.

Dr. Smith stepped into his time machine and set the date for the year 1850. As he traveled back in time, he saw horses and carriages on the streets and people wearing funny clothes. He was amazed!

But then, he remembered the warning his friend gave him. Every action he takes in the past will have a big effect on the present and future. Dr. Smith started to worry. What if he accidentally changed something and it caused a disaster in the present?

He decided to be very careful and not touch or change anything. But as he was walking down the street, he saw a little girl crying because she lost her doll. Dr. Smith felt bad and wanted to help her, so he gave her a new doll from his bag.

When he returned to the present, everything was different. The streets were filled with robots and the sky was purple. Dr. Smith realized that by giving the little girl a new doll, he changed the course of history and now the world was a strange place.

He learned his lesson and promised to never use the time machine again. From that day on, Dr. Smith focused on inventing things that would help people in the present, instead of traveling through time. The end.