Universe: It contains everything.
universe, molecular cloud, galaxy, star, planet, asteroid,atom
Universe -> galaxy -> star -> planet
Impossible to know because we don't know EVERY galaxy. The portion of the universe that we have to ability to see is extremely small compared to the entire universe.
Universe, galaxy,nebula,solar system, star, planet
biggest to smallest : universe, galaxy, star/solar system, planet, moon. The Universe is everything that exists and a galaxy is a cluster of billions of stars and then planets rotate around stars and moons rotate around planets.
universe, galaxy, planet, cell, organism, tissue, organ, ecosystem
Planet Solar System Galaxy Universe
Jupitor is the biggest planet and our galaxy is the a spiral galaxy:)
As of June 2014, Mars is the seventh biggest planet in the universe. The sie Mars is approximately 53% the size of the Earth.
In short it's the Sun but you probably didn't mean that. A dwarf planet like Pluto is among the biggest, or perhaps Saturn's moon Titan.
Universe, Cluster, Galaxy, Star, Planet NB: Some stars are smaller than planets.
Well i am doing a research on Mars and the biggest volcano would be Olympus Mons. But NASA is not sure if that might be in the whole galaxy! But take that answer for now, i will updated this answer later on!UPDATED