Molecular biology is a field of study that understands life phenomena at the molecular level.

He is an expert in biophysics.

I am majoring in developmental biology at university.

I am majoring in microbiology at university.

I am majoring in microbiology at university.

He is an expert in paleontology.

Astrobiology is a very interesting field of study.

He was holding my hand tightly.

He was running while holding a bag.

He always carries an umbrella around.