The shallow glass container used to prepare cultures in a science lab is called a Petri dish.

Here's why:

* Shallow: Petri dishes are designed to be flat and shallow to allow for easy observation of the cultures growing within.

* Glass: Petri dishes are typically made of glass, which is transparent and chemically inert, allowing for clear visualization of the cultures and minimizing contamination.

* Cultures: Petri dishes are used to grow bacterial cultures, fungal cultures, and even plant cells. They provide a controlled environment for the growth and study of microorganisms.

Let me know if you have any other questions!