I work as an astrophysicist at the Departmento de Fisica Teorica at
the Universidad Autonoma de Madrid
I use hydrodynamical galaxy formation simulations in a cosmological context in order to interpret observations of properties of galaxies, and how we can use these properties to probe the cosmological paradigm.
So what is the current cosmological paradigm?
Well.. the Universe began 13.7 Billion years ago in a Big Bang, and is comprised of 4% ordinary matter, which makes us and also the stars, planets and all things we can see, 23% dark matter, which only interacts via gravity, and 73% dark energy which makes the Universe expand at an ever increasing rate.
I find these online videos on the topic of cosmology interesting and instructional, and encourage you to take a look:
Dark Matter explained by cartoon (6 minutes)
explained by cartoon (7 minutes)
Extra Dimensions by cartoon (8 minutes)
D. Whiteson & J. Feng animated by J. Cham
A Universe from Nothing
Lawrance Krauss (64 minutes)