Patrick Speissegger of McMaster University presents a research seminar talk at the Institute for Advanced Study on multisummable series in the positive real directions. He starts from Tougeron's characterization, which lets such series be viewed as infinite sums of convergent power series with radii of convergence shrinking to zero, then describes joint work with Jean-Philippe Rolin and Tamara Servi replacing convergent power series with convergent generalized power series to obtain a larger multisummable class. That construction generates an o-minimal expansion whose further expansion by the exponential function defines restrictions of the Gamma and zeta functions on an unbounded interval. Speissegger also covers Ilgwon Seo's extension of the method using almost regular generalized power series, producing a Hardy field that represents a first step toward closing a remaining gap in Ilyashenko's proof of Dulac's problem. The talk assumes graduate-level familiarity with o-minimality and formal power series and runs about seventy minutes.