Question

What is in the cells of plants and in animals and all other eukaryotes

Answer 1

The are both eukaryotic cell
plant and animal cells are very similar because they are both eukaryotic cells. They both contain membrane-bound organelles such as the nucleus, mitochondria, endoplasmic reticulum, golgi apparatus, lysosomes, and peroxisomes.

Answer 2

eukaryote is any organism whose cells have a cell nucleus and other organelles enclosed within membranes. Eukaryotes belong to the domain Eukaryota or Eukarya, and can be single-celled or multi-cellular.

Or:

Eukaryotes are made up of eukaryotic cells. Eukaryotic cells contain a nucleus and membrane-bound organelles.