The friends were excited to use their time machine for a new purpose - helping people in need. They had seen so much during their time travels and knew that there were many people throughout history who could use their assistance.

Their first stop was the year 1945, during World War II. They arrived in a small village in Europe that had been devastated by the war. The villagers were struggling to rebuild their homes and their lives. Lily, Max, Ava, and Ben immediately got to work, using their knowledge of science to help the villagers rebuild faster and more efficiently.

They also used their time machine to bring back supplies and resources from the future, such as medicine and tools, to help the villagers. The grateful villagers thanked the friends for their help and the friends were happy to see the village thriving once again.

Next, they traveled to the year 1969, during the Civil Rights Movement in the United States. They met a group of activists who were fighting for equal rights and justice. The friends were inspired by their bravery and decided to use their time machine to spread awareness about the movement and help bring about change.

They traveled to different cities and showed people the future, where everyone was treated equally and with respect. The friends also used their time machine to bring back important documents and speeches from the future, which helped to educate and inspire people to join the movement.

Their final stop was in the year 2050, where they saw a world ravaged by climate change. The friends knew they had to do something to prevent this future from happening. They used their time machine to bring back advanced technology and knowledge from the future to help people understand the importance of taking care of the environment.

They also worked with scientists and leaders to come up with solutions to combat climate change. The friends were determined to make a difference and their efforts paid off as they saw the world slowly start to heal.

As they returned to their own time, the friends were proud of the impact they had made. They had used their time machine for a greater purpose and had helped people in need throughout history. Lily, Max, Ava, and Ben knew that they would continue to use their love for science to make the world a better place. The end.