The four elements common to all living organisms are carbon, hydrogen, nitrogen and:

1. Living matter is built overwhelmingly from a very short list of elements. 2. The four elements common to all living organisms are oxygen, carbon, hydrogen and nitrogen. 3. Sulfur and phosphorus appear too, but not in that core group of four. 4. Silicon is abundant in rock rather than in living tissue. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 2 'The Chemical Foundation of Life', sections 2.1-2.3_