Sure, until now only three U.S. Presidents have been formally impeached by Congress: Andrew Johnson, Bill Clinton, and Donald Trump. 1. Andrew Johnson: The impeachment of Andrew Johnson occurred in 1868, in the turbulent aftermath of the American Civil War. It arose from clear political conflicts between Johnson, who had assumed the presidency after Lincoln’s assassination, and the Republican-dominated Congress. The main charge against Johnson arose when he dismissed War Secretary Edwin M. Stanton against the wishes of Congress. Congress had previously passed the Tenure of Office Act expressly to protect Stanton, stating that a president could not dismiss certain officeholders without the Senate's approval. Ignoring this, Johnson removed Stanton, leading to his impeachment. However, the Senate, by a single vote, did not convict him. 2. Bill Clinton: Clinton was impeached by the House of Representatives in 1998. The first charges, perjury and obstruction of justice, resulted from a sexual harassment lawsuit filed by Paula Jones. Clinton was accused of lying about the nature of his affair with Monica Lewinsky, a White House intern, and subsequently obstructing justice by encouraging others to lie. The second charge, perjury before a grand jury, related to the same matter. However, when the case went to the Senate in 1999, neither charge resulted in a conviction, due to the votes falling short of the necessary two-thirds majority. 3. Donald Trump: He holds the distinction of being the only U.S. president to be impeached twice by the House of Representatives. - His first impeachment occurred in 2019. It focused on allegations that he sought help from foreign governments to discredit Joe Biden, his potential rival in the upcoming 2020 presidential election. The charges were abuse of power and obstruction of Congress. However, the Senate acquitted him of these charges in early 2020. - Trump's second impeachment occurred in 2021, following the violent attack on the U.S. Capitol by some of his supporters. As a result, he was charged with “incitement of insurrection” for his role in inciting the attack. His trial began on February 9, 2021, after he had left office. He was acquitted by the Senate on February 13, 2021. It's important to remember that impeachment by the House is essentially an accusation. The Senate then conducts a trial to determine whether to remove the president from office. To date, although three presidents have been impeached by the House, none have been removed from office by the Senate, as all were acquitted.