Question

1. when was the cell theory established?

1700s
1600s
1900s
1800s

Explanation:

The cell theory was established in the 1800s. In 1838, Matthias Schleiden proposed that all plants are made of cells. In 1839, Theodor Schwann proposed that all animals are made of cells. In 1855, Rudolf Virchow proposed that new cells come from pre - existing cells. These contributions together form the cell theory.

Answer:

1800s