Here's why:

* Protists are a diverse group of eukaryotic organisms (meaning they have a nucleus and other membrane-bound organelles) that don't fit neatly into other kingdoms like plants, animals, fungi, or bacteria.

* Some protists have characteristics of plant cells, such as the presence of chloroplasts for photosynthesis. This allows them to produce their own food like plants. Examples include algae.

* Other protists have characteristics of animal cells, such as the ability to move and consume food.

Therefore, Protista is the kingdom where you'll find microscopic organisms with plant-like characteristics.