Learn Dutch: Het is mogelijk om de proef morgen in het laboratorium te herhalen. - It is possible to repeat the experiment tomorrow in the laboratory.

Here, het acts as a "dummy subject" that points forward to the real action: repeating the experiment. To express this action, we use an om ... te clause. The word om starts the clause right after Het is mogelijk, and te herhalen (to repeat) is pushed to the very end of the sentence. All the extra details go between them.

Could I leave out om and just use te herhalen?

For this specific pattern (Het is [adjective] om ... te [verb]), using om is the standard and correct way to connect the dummy subject het to the action. While you might occasionally hear native speakers drop om in very casual speech, you should always include it when learning and writing.

Why is morgen placed before in het laboratorium?

This follows a classic Dutch word order rule: Time before Place. morgen tells us when (Time), so it must come before in het laboratorium, which tells us where (Place). Notice how both of these sit neatly inside the om ... te "bracket".

What kind of test or experiment is de proef?