Mitochondria are found in all .......cells.

Explanation

**Step-by-Step Solution:**

1. **Understanding Cell Types**: Begin by recognizing that there are two main types of cells: prokaryotic and eukaryotic. Prokaryotic cells are simpler and do not contain membrane-bound organelles, while eukaryotic cells are more complex and do contain these organelles.

2. **Identifying Mitochondria**: Mitochondria are known as the powerhouse of the cell because they produce energy in the form of ATP (adenosine triphosphate). They are membrane-bound organelles.

3. **Presence in Cell Types**: Mitochondria are present in all eukaryotic cells, which include both plant and animal cells. However, they are absent in prokaryotic cells (like bacteria), which do not have membrane-bound organelles.

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