The 1970s and 1980s saw the introduction of more mature themes and complex storylines, often reflecting the social and cultural upheavals of the time. Comics like The Dark Knight Returns (1986) and Watchmen (1986) pushed the boundaries of the medium, exploring issues like crime, corruption, and the nature of heroism. This period, known as the Bronze Age, also saw the rise of independent publishers like Frank Miller's Dark Horse Comics and Todd McFarlane's Image Comics.