Early Years
It was rumored that Natasha Romanova was somehow related to the last ruling czars of Russia, but this was never proven. Nothing else was known about her prior to World War II.
There are varying accounts of Romanova's early life. One account states that Nazis set the building Natasha was living in on fire in Stalingrad, and her mother threw her out the window to a Russian soldier before dying in the fire. The soldier’s name was Ivan Petrovitch, and he watched over Natasha for her entire life, remaining by her side as her chauffeur.
While under Ivan's protection, many adversaries attempted to attack her. Baron von Stucker abducted Natasha and presented her to the Hand in Madripoor. There, she was to become their Master Assassin until Captain America, Logan, and Ivan saved her. As Natasha grew and matured, she proved to be an amazing athlete and scholar, while gaining distinction in the USSR as a ballerina.
Another account establishes her as being raised from very early childhood by the U.S.S.R.'s "Black Widow Ops" program, rather than solely by Ivan Petrovitch. Petrovitch had taken her to Department X, with other young female orphans, where she is trained in combat and espionage at the covert "Red Room" facility. There, she is bio-technologically and psycho-technologically enhanced; an accounting that provides a rationale for her unusually long and youthful lifespan.
Regardless of which account is accurate, she was eventually arranged to marry Alexi Shostakov, a distinguished Soviet test pilot.
KGB
The Soviet government intelligence (KGB) decided that the skill set of this couple would make them superb special operatives, and split them up while Alexi was away on a mission. Trained as the Red Guardian, Alexi became the Soviet Union’s answer to the United States’ Captain America.
Natasha was told that her husband died in an experimental rocket crash, and was drafted into the KGB. She became their best operative from being trained in the infamous Red Room Academy, becoming excellent at fighting and information gathering. During this time she had some training under the Winter Soldier. It was there she was first dubbed the “Black Widow.”
The man named Logan resurfaced in America years later without any memory of his past, and in danger from Hydra assassins. She saved him and came upon him again when he stole the Red Storm Project from Russia alongside Carol Danvers and Ben Grimm.
Early Clashes with Iron Man
Black Widow was assigned to assist Boris Turgenov in the assassination of Professor Anton Vanko for defecting from their country by infiltrating Stark Industries in America. Tony Stark, the original Iron Man, continually foiled her schemes against Stark Industries. Romanova later met the novice archer Hawkeye and set him against Iron Man, and later helped Hawkeye battle Iron Man. Unfortunately, Hawkeye's association with Russian spies would label him a criminal in his early career. Black Widow and Hawkeye next clashed against the novice super-hero Spider-Man. They resumed their focus on Tony Stark, clashing with Iron Man twice more - the first being an attempt to raid Tony Stark's munitions plant.
When that mission ended in failure, she was taken back to Russia by her masters and given a new costume that allowed her to scale walls as well as a device that allowed her to fire lines to swing from. She once more attempted to get Hawkeye to help her destroy Iron Man. The pair almost succeeded, but when Black Widow was injured, Hawkeye retreated to get her to safety. During this period, Romanova was attempting to defect from the Soviet Union and began to feel love toward Hawkeye, weakening her loyalty to her country. When her employers learned the truth, they had her gunned down, sending her to a hospital, convincing Hawkeye to go straight and seek membership in the Avengers.
Association with the Avengers
Captured by her masters again and brainwashed, Black Widow was forced to hire the Swordsman and Power Man to destroy the Avengers. This plot eventually failed when the Avengers defeated both of the villains and Natasha shook off the effects of the brainwashing. Attempting to make amends with the group, she assisted them against the racist group known as the Sons of the Serpent.
Having been granted amnesty, Natasha made a bid for membership in the Avengers, aiding them in their battle against the Ultroids. She threatened to kill their leader Ixar if he did not leave the Earth, winning the victory, however Hawkeye covered up this fact so that she could get membership in the group even though she violated their code of ethics regarding killing. However when Nick Fury hired her to spy on her former master on behalf of S.H.I.E.L.D., she was be forced to decline membership with the Avengers and publicly broke off her relationship with Hawkeye. As part of her mission, the press branded her as a traitor, breaking Hawkeye's heart.
Arriving in China, the Black Widow was not easily trusted and subjected to the Psychotron device, a machine that could brainwash anyone. She proved to be too strong willed and had to be gassed and kept locked up. Learning that Natasha was now a prisoner of her former Communist masters, the Avengers traveled to China to rescue her, clashing with the Red Guardian, Natasha's ex-husband who was thought to be dead. The Avengers with the help of Natasha defeated the Communists plot to use the Psychotron against the western world. During the course of the battle Natasha was injured and the Red Guardian seemingly perished in the battle.
After time recovering in the hospital, Natasha returned to Avengers mansion and came to the decision to give up her career of costumed adventuring. However this proved to be short lived as she returned to super-heroics shortly thereafter, however her romance with Hawkeye became strained as he was usually too busy with Avengers business to pay attention to her.
Fed up with staying out of action, Black Widow accepted another assignment from S.H.I.E.L.D. to prevent Egghead from using an orbital platform to hold the world ransom. She was captured, prompting Hawkeye (who still loved her) to use Henry Pym's growth formula to become the new Goliath and rescue her. She aided the Avengers in stopping Egghead, although it ended in the seeming death of Egghead and Goliath's brother Barney. After a prolonged absence, the Black Widow eventually ended her relationship with Goliath.
Going Solo
Natasha was not be able to avoid super-heroics for long and, after designing a new sleek black costume and adapting her bracelets with electric "Widows Bites", she sought to prove herself a capable adventurer by besting Spider-Man in battle. Although Spider-Man was ill and not at his full capacity at the time, he was still able to beat the Widow, however she resolved to continue her career as a costumed adventurer.
She mostly clashed with underworld figures and costumed villains during this period, notably the Astrologer and Watchlord.
Partners with Daredevil
The Black Widow soon became a pawn manipulated by the computer known as Baal from the distant future Earth-71778. In that reality, mankind was wiped out and the past history of Daredevil and Black Widow played a crucial role. This ultimately lead to a long relationship and partnership between the two heroes, but it eventually came to an end.
While working with S.H.I.E.L.D., Black Widow was briefly captured as part of a HYDRA plot to infiltrate and brainwash the organization, causing her to regress to an old cover identity of teacher Nancy Rushman. Fortunately, she was discovered and rescued by Spider-Man, subsequently working with him, Nicky Fury, and Shang-Chi to defeat their plan; she even admitted that the Nancy identity was attracted to Spider-Man after the crisis was over, even if she preferred to retain her independence.
Avengers
During her more prominent stay with the Avengers, she was helpful in recruiting some personas, such as Bruce Banner into the ranks of S.H.I.E.L.D.. She also spent time fighting at their sides during the alien invasion, thankfully foiling Loki's plans and allowing Thor to return him to Asgard for punishment.