Karl Weierstrass was a German mathematician born on October 31, 1815, in Ostenfelde, Germany. He is often referred to as the "father of modern analysis" for his significant contributions to the field, particularly in the development of calculus and the theory of functions. Weierstrass introduced the concept of uniform convergence and formulated the Weierstrass approximation theorem, which states that any continuous function can be approximated by polynomials. Weierstrass also played a crucial role in the formalization of mathematical rigor. He was one of the first to use the epsilon-delta definition of limits, which is foundational in calculus. His work laid the groundwork for later mathematicians, including Bernhard Riemann and Henri Poincaré, influencing the study of real and complex analysis. Weierstrass passed away on February 19, 1897, leaving a lasting legacy in mathematics.