Learn Italian: Ho organizzato il viaggio stamattina. - I organized the trip this morning.

In spoken Italian, the most common past tense is the passato prossimo. Even though English often uses the simple past ("I organized"), Italian uses a two-part verb: a helper verb like ho (I have) plus the past participle organizzato (organized).

How is the past participle organizzato formed?

To make the past participle for regular verbs ending in -are, like organizzare (to organize), you drop the -are ending and replace it with -ato.

The translation for stamattina is "this morning", but shouldn't it use the word questa (this)?

Yes! Stamattina is simply a contraction of questa mattina (this morning). It is used so frequently in spoken Italian that it became a single, combined word. You will also see this pattern with stasera (this evening / tonight).

Why isn't the word io (I) at the start of the sentence?

Italian usually leaves out subject pronouns like io (I). The helper verb ho already tells us exactly who did the action, so you don't need to say io ho organizzato unless you want to emphasize that you were the one who did it, rather than someone else.