<div class="outer">
  <div class="grid__item">A</div>
  <div class="middle">
    <div class="grid__item">B1</div>
    <div class="inner">
      <div class="grid__item">B21</div>
      <div class="grid__item">B22</div>
    </div>
  </div>
  <div class="grid__item">C</div>
  <div class="grid__item">D</div>
</div>

<div class="warning">
  <p>Subgrid support required to get the most out of this pen</p>
</div>

@import url("https://fonts.googleapis.com/css2?family=Exo:wght@600&display=swap");

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  width: 100vw;
  min-height: 100vh;
  font-family: "Exo", Arial, sans-serif;
  background-color: #557;
  padding: 4rem 0;
}

.warning {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 2;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 0.5rem;
  background-color: #fed7d7;
  border-top: 1px solid #f56565;
  padding: 10px;
  color: #f56565;
}

@supports (grid-template-rows: subgrid) {
  .warning {
    display: none;
  }
}

.outer {
  height: calc(100vh - 8rem);
  max-width: 1024px;
  margin: 0 auto;
  outline: 4px solid #111;
  background: #333;
  padding: 1rem;
}

.middle {
  outline: 4px solid #111;
  background: #557;
  padding: 1rem;
}

.inner {
  outline: 4px solid #ff6c33;
  background: #ffcb00;
  padding: 1rem;
}

.grid__item {
  outline: 4px solid #111;
  background: #557;
  position: relative;
  padding: 1rem;
  color: #fff;
  display: flex;
  justify-content: center;
  align-items: center;
}

.outer {
  display: grid;
  grid-template-columns: [outer-edge] 1fr [main-start] 2fr [center] 3fr max-content [main-end];
  grid-template-areas: "gutter info info photos";
  gap: 1rem;
}
.middle {
  grid-column: main-start / main-end;
  display: grid;
  grid-template-rows: subgrid;
  grid-template-columns: subgrid;
}
.inner {
  grid-column: center / -1;
  display: grid;
  grid-template-rows: subgrid;
  grid-template-columns: subgrid;
}