He is majoring in soil science at university.

I am majoring in social science at university.

He is majoring in logic at university.

He is an expert in topology.

He is an expert in crystallography.

He is an expert in psychiatry.

This reaction has reached chemical equilibrium.

He is an expert in oenology and has a deep knowledge of wines from around the world.

He is majoring in history at university.

He is a world-famous scientist.