Can you briefly outline the events of 'Secret Invasion' and its place in the timeline?

'Secret Invasion' (2008) involves a covert alien invasion led by the Skrulls, who have infiltrated positions of power within the Marvel Universe. The storyline explores themes of paranoia and betrayal, and it significantly impacts the relationships between heroes and villains. It’s a key event in the Modern Age, demonstrating the ongoing threat posed by alien forces.