The furthest that humans have ever travelled is the Moon, and we haven’t stepped foot there since 1972. These humans, called Apollo astronauts, left things on the Moon like space buggies and flags. They are so small compared to the size of the Moon that we can’t see these from Earth even using the biggest telescopes – but space probes have been to the Moon since and taken pictures of some of the stuff we left of the surface.
The only other place which humans have travelled in space is to various space stations which have been in orbit round the Earth – the biggest of these is the International Space Station where astronauts still go. It is so big that it had to be built in space with lots of rockets with astronauts taking up new parts (called modules) and joining them together like a giant jigsaw puzzle.
There are plans for humans to go back to the Moon, and even travel to Mars. The company Space X are currently testing new rockets which would get us to Mars, but right now there are no rockets powerful enough to get people to Mars. It would take people around 7 months to make the journey to Mars, this compares to around 3 days to get to the Moon.
It’s unlikely that humans will ever be able to travel outside of our Solar System. It takes light (the fastest thing in the Universe) 4 years to reach us from the next closest star – a spaceship. Using any current technology, the fastest we could get to another star on a mission with humans would be 1000 years. We can however, send space probes and robots instead, these don’t need the same systems as people to keep them alive, and this means less space and weight. Even space probes would take 100s of years to reach another star. We can however, study other planets from here on Earth, or using telescopes which are in space but orbit close to Earth – using these we can search for life elsewhere in the Universe.